Fix #1618, Add asp- prefix to custom attributes of MVC tag helpers

- update XML docs to reflect new HTML / custom attribute separation
- update `Exception` messages to use new attribute names
- update MVC tag helper sample to use new custom attribute names
- add missing `<input/>` tag helper `throw`s test

nits:
- reword a few comments and messages for clarity and consistency
- use `<exception/>` sections to describe what's thrown
- add "Reviewers" comments about current throws
 - note `<a/>` and `<form/>` are slightly inconsistent with others: `throw`
   if unable to override specified `href` or `action` attributes; rest
   `throw` only if custom attributes are inconsistent e.g. `<input/>` with
   `asp-format` but no `asp-for`
- create test tag helpers after all property values are available

samples/TagHelperSample.Web/Views/Home/Create.cshtml

@@ -9,48 +9,47 @@
 <h2>Create</h2>
 
 @* anti-forgery is on by default *@
-@* form will special-case anything that looks like a URI i.e. contains a '/' or doesn't match an action *@
+@* <form/> tag helper will special-case only elements with an "asp-action" or "asp-anti-forgery" attribute. *@
-<form anti-forgery="false" action="Create">
+<form asp-anti-forgery="false" asp-action="Create">
     <div class="form-horizontal">
         @* validation summary tag helper will target just <div/> elements and append the list of errors *@
-        @* - i.e. this helper, like <select/> helper has ContentBehavior.Append *@
+        @* - i.e. this helper, like <select/> helper, has ContentBehavior.Append *@
-        @* helper does nothing if model is valid and (client-side validation is disabled or validation-summary="ModelOnly") *@
+        @* helper does nothing if model is valid and (client-side validation is disabled or asp-validation-summary="ModelOnly") *@
         @* don't need a bound attribute to match Html.ValidationSummary()'s headerTag parameter; users wrap message as they wish *@
         @* initially at least, will not remove the <div/> if list isn't generated *@
         @* - should helper remove the <div/> if list isn't generated? *@
         @* - (Html.ValidationSummary returns empty string despite non-empty message parameter) *@
         @* Acceptable values are: "None", "ModelOnly" and "All" *@
-        <div validation-summary="All" style="color:blue" id="validation_day" class="form-group">
+        <div asp-validation-summary="All" style="color:blue" id="validation_day" class="form-group">
             <span style="color:red">This is my message</span>
         </div>
 
         @* element will have correct name and id attributes for Id property. unusual part is the constant value. *@
         @* - the helper will _not_ override the user-specified "value" attribute *@
-        <input type="hidden" for="Id" value="0" />
+        <input type="hidden" asp-for="Id" value="0" />
 
         <div class="form-group">
-            @* no special-case for the "for" attribute; may eventually need to opt out on per-element basis here and in <form/> *@
+            @* no special-case for the "asp-for" attribute; now distinct from HTML "for" attribute. *@
-            <label for="Name" class="control-label col-md-2" style="color:blue" />
+            <label asp-for="Name" class="control-label col-md-2" style="color:blue" />
             <div class="col-md-10">
-                <input type="text" for="Name" style="color:blue" />
+                <input type="text" asp-for="Name" style="color:blue" />
-                <span validation-for="Name" style="color:blue" />
+                <span asp-validation-for="Name" style="color:blue" />
             </div>
         </div>
         <div class="form-group">
-            <label for="DateOfBirth" class="control-label col-md-2" />
+            <label asp-for="DateOfBirth" class="control-label col-md-2" />
             <div class="col-md-10">
-                @* will automatically infer type="date" (reused HTML attribute) and format="{0:yyyy-MM-dd}" (optional bound attribute) *@
+                @* will automatically infer type="date" (reused HTML attribute) and asp-format="{0:yyyy-MM-dd}" (optional bound attribute) *@
-                <input for="DateOfBirth" />
+                <input asp-for="DateOfBirth" />
-                <span validation-for="DateOfBirth">When were you born?</span>
+                <span asp-validation-for="DateOfBirth">When were you born?</span>
             </div>
         </div>
         <div class="form-group">
-            <label for="YearsEmployeed" class="control-label col-md-2" />
+            <label asp-for="YearsEmployeed" class="control-label col-md-2" />
             <div class="col-md-10">
                 @* <select/> tag helper has ContentBehavior.Append -- items render after static options *@
-                <select for="YearsEmployeed" items="(IEnumerable<SelectListItem>)ViewBag.Items" size="2" class="form-control">
+                <select asp-for="YearsEmployeed" asp-items="(IEnumerable<SelectListItem>)ViewBag.Items" size="2" class="form-control">
-                    @* schedule-wise option tag helper (which adds "selected" attribute to static <option/>s) comes after helpers *@
+                    @* Static use of "selected" attribute may cause HTML errors if in a single-selection <select/> *@
-                    @* - static use of "selected" attribute may cause HTML errors if in a single-selection <select/> *@
                     @* - @NTaylorMullen thinks <option/> tag helper could tell <select/> helper not to select anything from "items" *@
                     @* - wouldn't help if user selected one static <option/> and expression indicated another, especially one earlier in the <select/> *@
                     @* - may need a "default" bound parameter on the <select/> to avoid these cases and maintain "don't override" *@
@@ -68,20 +67,20 @@
 
                 @* targets only <span/> in Beta; does not support equivalent of Html.ValidationMessageFor()'s tag parameter *@
                 @* - may eventually either support additional tags e.g. <p/> and <div/> or all tags /> *@
-                <span validation-for="YearsEmployeed" />
+                <span asp-validation-for="YearsEmployeed" />
             </div>
         </div>
         <div class="form-group">
-            <label for="Blurb" class="control-label col-md-2" />
+            <label asp-for="Blurb" class="control-label col-md-2" />
             <div class="col-md-10">
-                <textarea rows="4" for="Blurb"></textarea>
+                <textarea rows="4" asp-for="Blurb"></textarea>
-                <span validation-for="Blurb" />
+                <span asp-validation-for="Blurb" />
             </div>
         </div>
 
         <div class="form-group">
             <div class="col-md-offset-2 col-md-10">
-                @* this <input/> lacks a "for" attribute and will not be changed by the <input/> tag helper *@
+                @* this <input/> lacks a "asp-for" attribute and will not be changed by the <input/> tag helper *@
                 <input type="submit" value="Create" class="btn btn-default" />
             </div>
         </div>
@@ -89,5 +88,5 @@
 </form>
 
 <div>
-    <a action="Index">Back to list</a>
+    <a asp-action="Index">Back to list</a>
 </div>

samples/TagHelperSample.Web/Views/Home/Edit.cshtml

@@ -6,27 +6,27 @@
 
 <form>
     <div class="form-horizontal">
-        <div validation-summary="All"/>
+        <div asp-validation-summary="All" />
-        <input type="hidden" for="Id" />
+        <input type="hidden" asp-for="Id" />
 
         <div class="form-group">
-            <label for="Name" class="control-label col-md-2" />
+            <label asp-for="Name" class="control-label col-md-2" />
             <div class="col-md-10">
-                <input type="text" for="Name" />
+                <input type="text" asp-for="Name" />
                 <span validation-for="Name" />
             </div>
         </div>
         <div class="form-group">
-            <label for="DateOfBirth" class="control-label col-md-2" />
+            <label asp-for="DateOfBirth" class="control-label col-md-2" />
             <div class="col-md-10">
-                <input type="date" for="DateOfBirth" format="{0:yyyy-MM-dd}" />
+                <input type="date" asp-for="DateOfBirth" asp-format="{0:yyyy-MM-dd}" />
-                <span validation-for="DateOfBirth" />
+                <span asp-validation-for="DateOfBirth" />
             </div>
         </div>
         <div class="form-group">
-            <label for="YearsEmployeed" class="control-label col-md-2" />
+            <label asp-for="YearsEmployeed" class="control-label col-md-2" />
             <div class="col-md-10">
-                <select for="YearsEmployeed" items="(IEnumerable<SelectListItem>)ViewBag.Items" size="2" class="form-control">
+                <select asp-for="YearsEmployeed" asp-items="(IEnumerable<SelectListItem>)ViewBag.Items" size="2" class="form-control">
                     <optgroup label="Newby">
                         <option value="0">Less than 1</option>
                         <option value="1">1</option>
@@ -37,14 +37,14 @@
                     <option value="5">5</option>
                     <option value="6">6</option>
                 </select>
-                <span validation-for="YearsEmployeed" />
+                <span asp-validation-for="YearsEmployeed" />
             </div>
         </div>
         <div class="form-group">
-            <label for="Blurb" class="control-label col-md-2" />
+            <label asp-for="Blurb" class="control-label col-md-2" />
             <div class="col-md-10">
-                <textarea rows="4" for="Blurb"></textarea>
+                <textarea rows="4" asp-for="Blurb"></textarea>
-                <span validation-for="Blurb" />
+                <span asp-validation-for="Blurb" />
             </div>
         </div>
 
@@ -57,5 +57,5 @@
 </form>
 
 <div>
-    <a action="Index">Back to list</a>
+    <a asp-action="Index">Back to list</a>
 </div>

samples/TagHelperSample.Web/Views/Home/Index.cshtml

@@ -9,36 +9,36 @@
         @for (var index = 0; index < Model.Count(); ++index)
         {
             <div class="form-group">
-                @Html.LabelFor(m => m[index].Name) @* [index].Name [0].Name *@
+                @Html.LabelFor(m => m[index].Name)
                 @Html.TextBoxFor(m => m[index].Name, htmlAttributes: new { disabled = "disabled", @readonly= "readonly" })
-                @*<label for="[index].Name" />
+                @*<label asp-for="[index].Name" />
-                <input type="text" for="[index].Name" disabled="disabled" readonly="readonly" />*@
+                <input type="text" asp-for="[index].Name" disabled="disabled" readonly="readonly" />*@
             </div>
             <div class="form-group">
                 @Html.LabelFor(m => m[index].DateOfBirth)
                 @Html.TextBoxFor(m => m[index].DateOfBirth, format: "{0:yyyy-MM-dd}", htmlAttributes: new { disabled = "disabled", @readonly = "readonly", type="date" })
-                @*<label for="[index].DateOfBirth" />
+                @*<label asp-for="[index].DateOfBirth" />
-                <input type="date" for="[index].DateOfBirth" disabled="disabled" readonly="readonly" />*@
+                <input type="date" asp-for="[index].DateOfBirth" disabled="disabled" readonly="readonly" />*@
             </div>
             <div class="form-group">
                 @Html.LabelFor(m => m[index].YearsEmployeed)
                 @Html.TextBoxFor(m => m[index].YearsEmployeed, htmlAttributes: new { disabled = "disabled", @readonly = "readonly", type="number" })
-                @*<label for="[index].YearsEmployeed" />
+                @*<label asp-for="[index].YearsEmployeed" />
-                <input type="number" for="[index].YearsEmployeed" disabled="disabled" readonly="readonly" />*@
+                <input type="number" asp-for="[index].YearsEmployeed" disabled="disabled" readonly="readonly" />*@
             </div>
             <div class="form-group">
                 @Html.LabelFor(m => m[index].Blurb)
                 @Html.TextAreaFor(m => m[index].Blurb, htmlAttributes: new { disabled = "disabled", @readonly = "readonly" })
-                @*<label for="[index].Blurb" />
+                @*<label asp-for="[index].Blurb" />
-                <textarea rows="4" for="[index].Blurb" disabled="disabled" readonly="readonly" />*@
+                <textarea rows="4" asp-for="[index].Blurb" disabled="disabled" readonly="readonly" />*@
             </div>
 
             <p>
-                <a action="Edit" route-id="@index">Edit</a>
+                <a asp-action="Edit" asp-route-id="@index">Edit</a>
             </p>
         }
     </div>
 }
 <p>
-    <a action="Create">Create New</a>
+    <a asp-action="Create">Create New</a>
 </p>

src/Microsoft.AspNet.Mvc.TagHelpers/AnchorTagHelper.cs

@@ -15,7 +15,13 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
     [TagName("a")]
     public class AnchorTagHelper : TagHelper
     {
-        private const string RouteAttributePrefix = "route-";
+        private const string ActionAttributeName = "asp-action";
+        private const string ControllerAttributeName = "asp-controller";
+        private const string FragmentAttributeName = "asp-fragment";
+        private const string HostAttributeName = "asp-host";
+        private const string ProtocolAttributeName = "asp-protocol";
+        private const string RouteAttributeName = "asp-route";
+        private const string RouteAttributePrefix = "asp-route-";
         private const string Href = "href";
 
         // Protected to ensure subclasses are correctly activated. Internal for ease of use when testing.
@@ -26,27 +32,32 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// The name of the action method.
         /// </summary>
         /// <remarks>Must be <c>null</c> if <see cref="Route"/> is non-<c>null</c>.</remarks>
+        [HtmlAttributeName(ActionAttributeName)]
         public string Action { get; set; }
 
         /// <summary>
         /// The name of the controller.
         /// </summary>
         /// <remarks>Must be <c>null</c> if <see cref="Route"/> is non-<c>null</c>.</remarks>
+        [HtmlAttributeName(ControllerAttributeName)]
         public string Controller { get; set; }
 
         /// <summary>
         /// The protocol for the URL, such as &quot;http&quot; or &quot;https&quot;.
         /// </summary>
+        [HtmlAttributeName(ProtocolAttributeName)]
         public string Protocol { get; set; }
 
         /// <summary>
         /// The host name.
         /// </summary>
+        [HtmlAttributeName(HostAttributeName)]
         public string Host { get; set; }
 
         /// <summary>
         /// The URL fragment name.
         /// </summary>
+        [HtmlAttributeName(FragmentAttributeName)]
         public string Fragment { get; set; }
 
         /// <summary>
@@ -55,17 +66,22 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// <remarks>
         /// Must be <c>null</c> if <see cref="Action"/> or <see cref="Controller"/> is non-<c>null</c>.
         /// </remarks>
+        [HtmlAttributeName(RouteAttributeName)]
         public string Route { get; set; }
 
         /// <inheritdoc />
-        /// <remarks>Does nothing if user provides an "href" attribute. Throws an
+        /// <remarks>Does nothing if user provides an <c>href</c> attribute.</remarks>
-        /// <see cref="InvalidOperationException"/> if "href" attribute is provided and <see cref="Action"/>,
+        /// <exception cref="InvalidOperationException">
-        /// <see cref="Controller"/>, or <see cref="Route"/> are non-<c>null</c>.</remarks>
+        /// Thrown if <c>href</c> attribute is provided and <see cref="Action"/>, <see cref="Controller"/>,
+        /// <see cref="Fragment"/>, <see cref="Host"/>, <see cref="Protocol"/>, or <see cref="Route"/> are
+        /// non-<c>null</c> or if the user provided <c>asp-route-*</c> attributes. Also thrown if <see cref="Route"/>
+        /// and one or both of <see cref="Action"/> and <see cref="Controller"/> are non-<c>null</c>.
+        /// </exception>
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
             var routePrefixedAttributes = output.FindPrefixedAttributes(RouteAttributePrefix);
 
-            // If there's an "href" on the tag it means it's being used as a normal anchor.
+            // If "href" is already set, it means the user is attempting to use a normal anchor.
             if (output.Attributes.ContainsKey(Href))
             {
                 if (Action != null ||
@@ -77,15 +93,16 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     routePrefixedAttributes.Any())
                 {
                     // User specified an href and one of the bound attributes; can't determine the href attribute.
+                    // Reviewers: Should this instead ignore the helper-specific attributes?
                     throw new InvalidOperationException(
-                        Resources.FormatAnchorTagHelper_CannotOverrideSpecifiedHref(
+                        Resources.FormatAnchorTagHelper_CannotOverrideHref(
                             "<a>",
-                            nameof(Action).ToLowerInvariant(),
+                            ActionAttributeName,
-                            nameof(Controller).ToLowerInvariant(),
+                            ControllerAttributeName,
-                            nameof(Route).ToLowerInvariant(),
+                            RouteAttributeName,
-                            nameof(Protocol).ToLowerInvariant(),
+                            ProtocolAttributeName,
-                            nameof(Host).ToLowerInvariant(),
+                            HostAttributeName,
-                            nameof(Fragment).ToLowerInvariant(),
+                            FragmentAttributeName,
                             RouteAttributePrefix,
                             Href));
                 }
@@ -112,9 +129,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     throw new InvalidOperationException(
                         Resources.FormatAnchorTagHelper_CannotDetermineHrefRouteActionOrControllerSpecified(
                             "<a>",
-                            nameof(Route).ToLowerInvariant(),
+                            RouteAttributeName,
-                            nameof(Action).ToLowerInvariant(),
+                            ActionAttributeName,
-                            nameof(Controller).ToLowerInvariant(),
+                            ControllerAttributeName,
                             Href));
                 }
                 else

src/Microsoft.AspNet.Mvc.TagHelpers/FormTagHelper.cs

@@ -16,7 +16,11 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
     [ContentBehavior(ContentBehavior.Append)]
     public class FormTagHelper : TagHelper
     {
-        private const string RouteAttributePrefix = "route-";
+        private const string ActionAttributeName = "asp-action";
+        private const string AntiForgeryAttributeName = "asp-anti-forgery";
+        private const string ControllerAttributeName = "asp-controller";
+        private const string RouteAttributePrefix = "asp-route-";
+        private const string HtmlActionAttributeName = "action";
 
         // Protected to ensure subclasses are correctly activated. Internal for ease of use when testing.
         [Activate]
@@ -29,14 +33,13 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// <summary>
         /// The name of the action method.
         /// </summary>
-        /// <remarks>
+        [HtmlAttributeName(ActionAttributeName)]
-        /// If value contains a '/' this <see cref="ITagHelper"/> will do nothing.
-        /// </remarks>
         public string Action { get; set; }
 
         /// <summary>
         /// The name of the controller.
         /// </summary>
+        [HtmlAttributeName(ControllerAttributeName)]
         public string Controller { get; set; }
 
         /// <summary>
@@ -45,41 +48,45 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         public string Method { get; set; }
 
         /// <summary>
-        /// Whether the anti-forgery token should be generated. Defaults to <c>true</c> if <see cref="Action"/> is not
+        /// Whether the anti-forgery token should be generated. 
-        /// a URL, <c>false</c> otherwise.
         /// </summary>
-        [HtmlAttributeName("anti-forgery")]
+        /// <value>Defaults to <c>false</c> if user provides an <c>action</c> attribute; <c>true</c> otherwise.</value>
+        [HtmlAttributeName(AntiForgeryAttributeName)]
         public bool? AntiForgery { get; set; }
 
         /// <inheritdoc />
-        /// <remarks>Does nothing if <see cref="Action"/> contains a '/'.</remarks>
+        /// <remarks>At most adds an anti-forgery token if user provides an <c>action</c> attribute.</remarks>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if <c>action</c> attribute is provided and <see cref="Action"/> or <see cref="Controller"/> are
+        /// non-<c>null</c> or if the user provided <c>asp-route-*</c> attributes.
+        /// </exception>
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
             bool antiForgeryDefault = true;
-
             var routePrefixedAttributes = output.FindPrefixedAttributes(RouteAttributePrefix);
 
-            // If Action contains a '/' it means the user is attempting to use the FormTagHelper as a normal form.
+            // If "action" is already set, it means the user is attempting to use a normal <form>.
-            if (Action != null && Action.Contains('/'))
+            if (output.Attributes.ContainsKey(HtmlActionAttributeName))
             {
-                if (Controller != null || routePrefixedAttributes.Any())
+                if (Action != null || Controller != null || routePrefixedAttributes.Any())
                 {
-                    // We don't know how to generate a form action since a Controller attribute was also provided.
+                    // User also specified bound attributes we cannot use.
+                    // Reviewers: Should this instead ignore the helper-specific attributes -- only change
+                    // antiForgeryDefault?
                     throw new InvalidOperationException(
-                        Resources.FormatFormTagHelper_CannotDetermineAction(
+                        Resources.FormatFormTagHelper_CannotOverrideAction(
                             "<form>",
-                            nameof(Action).ToLowerInvariant(),
+                            HtmlActionAttributeName,
-                            nameof(Controller).ToLowerInvariant(),
+                            ActionAttributeName,
+                            ControllerAttributeName,
                             RouteAttributePrefix));
                 }
 
-                // User is using the FormTagHelper like a normal <form> tag, anti-forgery default should be false to
+                // User is using the FormTagHelper like a normal <form> tag. Anti-forgery default should be false to
-                // not force the anti-forgery token onto the user.
+                // not force the anti-forgery token on the user.
                 antiForgeryDefault = false;
 
-                // Restore Action, Method and Route HTML attributes if they were provided, user wants non-TagHelper <form>.
+                // Restore method attribute.
-                output.CopyHtmlAttribute(nameof(Action), context);
-
                 if (Method != null)
                 {
                     output.CopyHtmlAttribute(nameof(Method), context);

src/Microsoft.AspNet.Mvc.TagHelpers/InputTagHelper.cs

@@ -13,11 +13,14 @@ using Microsoft.AspNet.Razor.TagHelpers;
 namespace Microsoft.AspNet.Mvc.TagHelpers
 {
     /// <summary>
-    /// <see cref="ITagHelper"/> implementation targeting &lt;input&gt; elements.
+    /// <see cref="ITagHelper"/> implementation targeting &lt;input&gt; elements with an <c>asp-for</c> attribute.
     /// </summary>
     [ContentBehavior(ContentBehavior.Replace)]
     public class InputTagHelper : TagHelper
     {
+        private const string ForAttributeName = "asp-for";
+        private const string FormatAttributeName = "asp-format";
+
         // Mapping from datatype names and data annotation hints to values for the <input/> element's "type" attribute.
         private static readonly Dictionary<string, string> _defaultInputTypes =
             new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase)
@@ -64,6 +67,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// <summary>
         /// An expression to be evaluated against the current model.
         /// </summary>
+        [HtmlAttributeName(ForAttributeName)]
         public ModelExpression For { get; set; }
 
         /// <summary>
@@ -76,6 +80,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// <see cref="InputTypeName"/> is "String". That is, <see cref="Format"/> is used when calling
         /// <see cref="IHtmlGenerator.GenerateTextBox"/>.
         /// </remarks>
+        [HtmlAttributeName(FormatAttributeName)]
         public string Format { get; set; }
 
         /// <summary>
@@ -99,7 +104,10 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         public string Value { get; set; }
 
         /// <inheritdoc />
-        /// <remarks>Does nothing if <see cref="For"/> is <c>null</c></remarks>
+        /// <remarks>Does nothing if <see cref="For"/> is <c>null</c>.</remarks>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if <see cref="Format"/> is non-<c>null</c> but <see cref="For"/> is <c>null</c>.
+        /// </exception>
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
             // Pass through attributes that are also well-known HTML attributes. Must be done prior to any copying
@@ -117,12 +125,13 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             if (For == null)
             {
                 // Regular HTML <input/> element. Just make sure Format wasn't specified.
+                // Reviewers: Should this instead ignore the unused helper-specific attribute?
                 if (Format != null)
                 {
                     throw new InvalidOperationException(Resources.FormatInputTagHelper_UnableToFormat(
                         "<input>",
-                        nameof(For).ToLowerInvariant(),
+                        ForAttributeName,
-                        nameof(Format).ToLowerInvariant()));
+                        FormatAttributeName));
                 }
             }
             else
@@ -134,7 +143,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 {
                     throw new InvalidOperationException(Resources.FormatTagHelpers_NoProvidedMetadata(
                         "<input>",
-                        nameof(For).ToLowerInvariant(),
+                        ForAttributeName,
                         nameof(IModelMetadataProvider),
                         For.Name));
                 }
@@ -210,7 +219,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             {
                 throw new InvalidOperationException(Resources.FormatInputTagHelper_InvalidExpressionResult(
                     "<input>",
-                    nameof(For).ToLowerInvariant(),
+                    ForAttributeName,
                     metadata.RealModelType.FullName,
                     typeof(bool).FullName,
                     "type",

src/Microsoft.AspNet.Mvc.TagHelpers/LabelTagHelper.cs

@@ -8,11 +8,13 @@ using Microsoft.AspNet.Razor.TagHelpers;
 namespace Microsoft.AspNet.Mvc.TagHelpers
 {
     /// <summary>
-    /// <see cref="ITagHelper"/> implementation targeting &lt;label&gt; elements with <c>for</c> attributes.
+    /// <see cref="ITagHelper"/> implementation targeting &lt;label&gt; elements with an <c>asp-for</c> attribute.
     /// </summary>
     [ContentBehavior(ContentBehavior.Modify)]
     public class LabelTagHelper : TagHelper
     {
+        private const string ForAttributeName = "asp-for";
+
         // Protected to ensure subclasses are correctly activated. Internal for ease of use when testing.
         [Activate]
         protected internal ViewContext ViewContext { get; set; }
@@ -24,9 +26,11 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// <summary>
         /// An expression to be evaluated against the current model.
         /// </summary>
+        [HtmlAttributeName(ForAttributeName)]
         public ModelExpression For { get; set; }
 
         /// <inheritdoc />
+        /// <remarks>Does nothing if <see cref="For"/> is <c>null</c>.</remarks>
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
             if (For != null)

src/Microsoft.AspNet.Mvc.TagHelpers/Properties/Resources.Designer.cs

@@ -11,7 +11,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             = new ResourceManager("Microsoft.AspNet.Mvc.TagHelpers.Resources", typeof(Resources).GetTypeInfo().Assembly);
 
         /// <summary>
-        /// Cannot determine an '{4}' for {0}. An {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.
+        /// Cannot determine an '{4}' attribute for {0}. An {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.
         /// </summary>
         internal static string AnchorTagHelper_CannotDetermineHrefRouteActionOrControllerSpecified
         {
@@ -19,7 +19,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         }
 
         /// <summary>
-        /// Cannot determine an '{4}' for {0}. An {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.
+        /// Cannot determine an '{4}' attribute for {0}. An {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.
         /// </summary>
         internal static string FormatAnchorTagHelper_CannotDetermineHrefRouteActionOrControllerSpecified(object p0, object p1, object p2, object p3, object p4)
         {
@@ -27,19 +27,35 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         }
 
         /// <summary>
-        /// Cannot determine an '{8}' for {0}. An {0} with a specified '{8}' must not have attributes starting with '{7}' or an '{1}', '{2}', '{3}', '{4}', '{5}', or '{6}' attribute.
+        /// Cannot override the '{8}' attribute for {0}. An {0} with a specified '{8}' must not have attributes starting with '{7}' or an '{1}', '{2}', '{3}', '{4}', '{5}', or '{6}' attribute.
         /// </summary>
-        internal static string AnchorTagHelper_CannotOverrideSpecifiedHref
+        internal static string AnchorTagHelper_CannotOverrideHref
         {
-            get { return GetString("AnchorTagHelper_CannotOverrideSpecifiedHref"); }
+            get { return GetString("AnchorTagHelper_CannotOverrideHref"); }
         }
 
         /// <summary>
-        /// Cannot determine an '{8}' for {0}. An {0} with a specified '{8}' must not have attributes starting with '{7}' or an '{1}', '{2}', '{3}', '{4}', '{5}', or '{6}' attribute.
+        /// Cannot override the '{8}' attribute for {0}. An {0} with a specified '{8}' must not have attributes starting with '{7}' or an '{1}', '{2}', '{3}', '{4}', '{5}', or '{6}' attribute.
         /// </summary>
-        internal static string FormatAnchorTagHelper_CannotOverrideSpecifiedHref(object p0, object p1, object p2, object p3, object p4, object p5, object p6, object p7, object p8)
+        internal static string FormatAnchorTagHelper_CannotOverrideHref(object p0, object p1, object p2, object p3, object p4, object p5, object p6, object p7, object p8)
         {
-            return string.Format(CultureInfo.CurrentCulture, GetString("AnchorTagHelper_CannotOverrideSpecifiedHref"), p0, p1, p2, p3, p4, p5, p6, p7, p8);
+            return string.Format(CultureInfo.CurrentCulture, GetString("AnchorTagHelper_CannotOverrideHref"), p0, p1, p2, p3, p4, p5, p6, p7, p8);
+        }
+
+        /// <summary>
+        /// Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{4}' or an '{2}' or '{3}' attribute.
+        /// </summary>
+        internal static string FormTagHelper_CannotOverrideAction
+        {
+            get { return GetString("FormTagHelper_CannotOverrideAction"); }
+        }
+
+        /// <summary>
+        /// Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{4}' or an '{2}' or '{3}' attribute.
+        /// </summary>
+        internal static string FormatFormTagHelper_CannotOverrideAction(object p0, object p1, object p2, object p3, object p4)
+        {
+            return string.Format(CultureInfo.CurrentCulture, GetString("FormTagHelper_CannotOverrideAction"), p0, p1, p2, p3, p4);
         }
 
         /// <summary>
@@ -90,22 +106,6 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             return string.Format(CultureInfo.CurrentCulture, GetString("InputTagHelper_ValueRequired"), p0, p1, p2, p3);
         }
 
-        /// <summary>
-        /// Cannot determine an '{1}' for {0}. A {0} with a URL-based '{1}' must not have attributes starting with '{3}' or a '{2}' attribute.
-        /// </summary>
-        internal static string FormTagHelper_CannotDetermineAction
-        {
-            get { return GetString("FormTagHelper_CannotDetermineAction"); }
-        }
-
-        /// <summary>
-        /// Cannot determine an '{1}' for {0}. A {0} with a URL-based '{1}' must not have attributes starting with '{3}' or a '{2}' attribute.
-        /// </summary>
-        internal static string FormatFormTagHelper_CannotDetermineAction(object p0, object p1, object p2, object p3)
-        {
-            return string.Format(CultureInfo.CurrentCulture, GetString("FormTagHelper_CannotDetermineAction"), p0, p1, p2, p3);
-        }
-
         /// <summary>
         /// Cannot determine body for {0}. '{2}' must be null if '{1}' is null.
         /// </summary>

src/Microsoft.AspNet.Mvc.TagHelpers/Resources.resx

@@ -118,10 +118,13 @@
     <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
   </resheader>
   <data name="AnchorTagHelper_CannotDetermineHrefRouteActionOrControllerSpecified" xml:space="preserve">
-    <value>Cannot determine an '{4}' for {0}. An {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.</value>
+    <value>Cannot determine an '{4}' attribute for {0}. An {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.</value>
   </data>
-  <data name="AnchorTagHelper_CannotOverrideSpecifiedHref" xml:space="preserve">
+  <data name="AnchorTagHelper_CannotOverrideHref" xml:space="preserve">
-    <value>Cannot determine an '{8}' for {0}. An {0} with a specified '{8}' must not have attributes starting with '{7}' or an '{1}', '{2}', '{3}', '{4}', '{5}', or '{6}' attribute.</value>
+    <value>Cannot override the '{8}' attribute for {0}. An {0} with a specified '{8}' must not have attributes starting with '{7}' or an '{1}', '{2}', '{3}', '{4}', '{5}', or '{6}' attribute.</value>
+  </data>
+  <data name="FormTagHelper_CannotOverrideAction" xml:space="preserve">
+    <value>Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{4}' or an '{2}' or '{3}' attribute.</value>
   </data>
   <data name="InputTagHelper_InvalidExpressionResult" xml:space="preserve">
     <value>Unexpected '{1}' expression result type '{2}' for {0}. '{1}' must be of type '{3}' if '{4}' is '{5}'.</value>
@@ -132,9 +135,6 @@
   <data name="InputTagHelper_ValueRequired" xml:space="preserve">
     <value>'{1}' must not be null for {0} if '{2}' is '{3}'.</value>
   </data>
-  <data name="FormTagHelper_CannotDetermineAction" xml:space="preserve">
-    <value>Cannot determine an '{1}' for {0}. A {0} with a URL-based '{1}' must not have attributes starting with '{3}' or a '{2}' attribute.</value>
-  </data>
   <data name="SelectTagHelper_CannotDetermineContentWhenOnlyItemsSpecified" xml:space="preserve">
     <value>Cannot determine body for {0}. '{2}' must be null if '{1}' is null.</value>
   </data>

src/Microsoft.AspNet.Mvc.TagHelpers/SelectTagHelper.cs

@@ -13,11 +13,14 @@ using Microsoft.AspNet.Razor.TagHelpers;
 namespace Microsoft.AspNet.Mvc.TagHelpers
 {
     /// <summary>
-    /// <see cref="ITagHelper"/> implementation targeting &lt;select&gt; elements.
+    /// <see cref="ITagHelper"/> implementation targeting &lt;select&gt; elements with an <c>asp-for</c> attribute.
     /// </summary>
     [ContentBehavior(ContentBehavior.Append)]
     public class SelectTagHelper : TagHelper
     {
+        private const string ForAttributeName = "asp-for";
+        private const string ItemsAttributeName = "asp-items";
+
         /// <summary>
         /// Key used for selected values in <see cref="FormContext.FormData"/>.
         /// </summary>
@@ -39,6 +42,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// <summary>
         /// An expression to be evaluated against the current model.
         /// </summary>
+        [HtmlAttributeName(ForAttributeName)]
         public ModelExpression For { get; set; }
 
         /// <summary>
@@ -55,21 +59,26 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// A collection of <see cref="SelectListItem"/> objects used to populate the &lt;select&gt; element with
         /// &lt;optgroup&gt; and &lt;option&gt; elements.
         /// </summary>
+        [HtmlAttributeName(ItemsAttributeName)]
         public IEnumerable<SelectListItem> Items { get; set; }
 
         /// <inheritdoc />
         /// <remarks>Does nothing if <see cref="For"/> is <c>null</c>.</remarks>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if <see cref="Items"/> is non-<c>null</c> but <see cref="For"/> is <c>null</c>.
+        /// </exception>
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
             if (For == null)
             {
                 // Regular HTML <select/> element. Just make sure Items wasn't specified.
+                // Reviewers: Should this instead ignore the unused helper-specific attribute?
                 if (Items != null)
                 {
                     var message = Resources.FormatSelectTagHelper_CannotDetermineContentWhenOnlyItemsSpecified(
                         "<select>",
-                        nameof(For).ToLowerInvariant(),
+                        ForAttributeName,
-                        nameof(Items).ToLowerInvariant());
+                        ItemsAttributeName);
                     throw new InvalidOperationException(message);
                 }
 
@@ -88,7 +97,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 {
                     throw new InvalidOperationException(Resources.FormatTagHelpers_NoProvidedMetadata(
                         "<select>",
-                        nameof(For).ToLowerInvariant(),
+                        ForAttributeName,
                         nameof(IModelMetadataProvider),
                         For.Name));
                 }

src/Microsoft.AspNet.Mvc.TagHelpers/TextAreaTagHelper.cs

@@ -8,11 +8,13 @@ using Microsoft.AspNet.Razor.TagHelpers;
 namespace Microsoft.AspNet.Mvc.TagHelpers
 {
     /// <summary>
-    /// <see cref="ITagHelper"/> implementation targeting &lt;textarea&gt; elements.
+    /// <see cref="ITagHelper"/> implementation targeting &lt;textarea&gt; elements with an <c>asp-for</c> attribute.
     /// </summary>
     [ContentBehavior(ContentBehavior.Replace)]
     public class TextAreaTagHelper : TagHelper
     {
+        private const string ForAttributeName = "asp-for";
+
         // Protected to ensure subclasses are correctly activated. Internal for ease of use when testing.
         [Activate]
         protected internal IHtmlGenerator Generator { get; set; }
@@ -24,10 +26,11 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// <summary>
         /// An expression to be evaluated against the current model.
         /// </summary>
+        [HtmlAttributeName(ForAttributeName)]
         public ModelExpression For { get; set; }
 
         /// <inheritdoc />
-        /// <remarks>Does nothing unless user binds "for" attribute in Razor source.</remarks>
+        /// <remarks>Does nothing if <see cref="For"/> is <c>null</c>.</remarks>
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
             if (For != null)

src/Microsoft.AspNet.Mvc.TagHelpers/ValidationMessageTagHelper.cs

@@ -8,12 +8,15 @@ using Microsoft.AspNet.Razor.TagHelpers;
 namespace Microsoft.AspNet.Mvc.TagHelpers
 {
     /// <summary>
-    /// <see cref="ITagHelper"/> implementation targeting &lt;span&gt; elements with <c>validation-for</c> attributes.
+    /// <see cref="ITagHelper"/> implementation targeting &lt;span&gt; elements with an <c>asp-validation-for</c>
+    /// attribute.
     /// </summary>
     [TagName("span")]
     [ContentBehavior(ContentBehavior.Modify)]
     public class ValidationMessageTagHelper : TagHelper
     {
+        private const string ValidationForAttributeName = "asp-validation-for";
+
         // Protected to ensure subclasses are correctly activated. Internal for ease of use when testing.
         [Activate]
         protected internal ViewContext ViewContext { get; set; }
@@ -25,10 +28,11 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// <summary>
         /// Name to be validated on the current model.
         /// </summary>
-        [HtmlAttributeName("validation-for")]
+        [HtmlAttributeName(ValidationForAttributeName)]
         public ModelExpression For { get; set; }
 
         /// <inheritdoc />
+        /// <remarks>Does nothing if <see cref="For"/> is <c>null</c>.</remarks>
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
             if (For != null)

src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummaryTagHelper.cs

@@ -9,13 +9,15 @@ using Microsoft.AspNet.Razor.TagHelpers;
 namespace Microsoft.AspNet.Mvc.TagHelpers
 {
     /// <summary>
-    /// <see cref="ITagHelper"/> implementation targeting &lt;div&gt; elements with a <c>validation-summary</c>
+    /// <see cref="ITagHelper"/> implementation targeting &lt;div&gt; elements with an <c>asp-validation-summary</c>
     /// attribute.
     /// </summary>
     [TagName("div")]
     [ContentBehavior(ContentBehavior.Append)]
     public class ValidationSummaryTagHelper : TagHelper
     {
+        private const string ValidationSummaryAttributeName = "asp-validation-summary";
+
         // Protected to ensure subclasses are correctly activated. Internal for ease of use when testing.
         [Activate]
         protected internal ViewContext ViewContext { get; set; }
@@ -29,11 +31,14 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         /// If <c>All</c> or <c>ModelOnly</c>, appends a validation summary. Acceptable values are defined by the
         /// <see cref="ValidationSummary"/> enum.
         /// </summary>
-        [HtmlAttributeName("validation-summary")]
+        [HtmlAttributeName(ValidationSummaryAttributeName)]
         public string ValidationSummaryValue { get; set; }
 
         /// <inheritdoc />
-        /// Does nothing if <see cref="ValidationSummaryValue"/> is <c>null</c>, empty or "None".
+        /// <remarks>Does nothing if <see cref="ValidationSummaryValue"/> is <c>null</c>, empty or "None".</remarks>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if <see cref="ValidationSummaryValue"/> is not a valid <see cref="ValidationSummary"/> value.
+        /// </exception>
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
             if (!string.IsNullOrEmpty(ValidationSummaryValue))
@@ -44,7 +49,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     throw new InvalidOperationException(
                         Resources.FormatTagHelpers_InvalidValue_ThreeAcceptableValues(
                             "<div>",
-                            "validation-summary",
+                            ValidationSummaryAttributeName,
                             ValidationSummaryValue,
                             ValidationSummary.All,
                             ValidationSummary.ModelOnly,

test/Microsoft.AspNet.Mvc.TagHelpers.Test/AnchorTagHelperTest.cs

@@ -20,32 +20,24 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Arrange
             var expectedTagName = "not-a";
             var metadataProvider = new DataAnnotationsModelMetadataProvider();
-            var anchorTagHelper = new AnchorTagHelper
-            {
-                Action = "index",
-                Controller = "home",
-                Fragment = "hello=world",
-                Host = "contoso.com",
-                Protocol = "http"
-            };
 
             var tagHelperContext = new TagHelperContext(
                 allAttributes: new Dictionary<string, object>
                 {
                     { "id", "myanchor" },
-                    { "route-foo", "bar" },
+                    { "asp-route-foo", "bar" },
-                    { "action", "index" },
+                    { "asp-action", "index" },
-                    { "controller", "home" },
+                    { "asp-controller", "home" },
-                    { "fragment", "hello=world" },
+                    { "asp-fragment", "hello=world" },
-                    { "host", "contoso.com" },
+                    { "asp-host", "contoso.com" },
-                    { "protocol", "http" }
+                    { "asp-protocol", "http" }
                 });
             var output = new TagHelperOutput(
                 expectedTagName,
                 attributes: new Dictionary<string, string>
                 {
                     { "id", "myanchor" },
-                    { "route-foo", "bar" },
+                    { "asp-route-foo", "bar" },
                 },
                 content: "Something");
 
@@ -64,7 +56,15 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var viewContext = TestableHtmlGenerator.GetViewContext(model: null,
                                                                    htmlGenerator: htmlGenerator,
                                                                    metadataProvider: metadataProvider);
-            anchorTagHelper.Generator = htmlGenerator;
+            var anchorTagHelper = new AnchorTagHelper
+            {
+                Action = "index",
+                Controller = "home",
+                Fragment = "hello=world",
+                Generator = htmlGenerator,
+                Host = "contoso.com",
+                Protocol = "http",
+            };
 
             // Act
             await anchorTagHelper.ProcessAsync(tagHelperContext, output);
@@ -83,13 +83,6 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         public async Task ProcessAsync_CallsIntoRouteLinkWithExpectedParameters()
         {
             // Arrange
-            var anchorTagHelper = new AnchorTagHelper
-            {
-                Route = "Default",
-                Protocol = "http",
-                Host = "contoso.com",
-                Fragment = "hello=world"
-            };
             var context = new TagHelperContext(
                 allAttributes: new Dictionary<string, object>());
             var output = new TagHelperOutput(
@@ -103,7 +96,14 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     string.Empty, "Default", "http", "contoso.com", "hello=world", null, null))
                 .Returns(new TagBuilder("a"))
                 .Verifiable();
-            anchorTagHelper.Generator = generator.Object;
+            var anchorTagHelper = new AnchorTagHelper
+            {
+                Fragment = "hello=world",
+                Generator = generator.Object,
+                Host = "contoso.com",
+                Protocol = "http",
+                Route = "Default",
+            };
 
             // Act & Assert
             await anchorTagHelper.ProcessAsync(context, output);
@@ -117,14 +117,6 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         public async Task ProcessAsync_CallsIntoActionLinkWithExpectedParameters()
         {
             // Arrange
-            var anchorTagHelper = new AnchorTagHelper
-            {
-                Action = "Index",
-                Controller = "Home",
-                Protocol = "http",
-                Host = "contoso.com",
-                Fragment = "hello=world"
-            };
             var context = new TagHelperContext(
                 allAttributes: new Dictionary<string, object>());
             var output = new TagHelperOutput(
@@ -138,7 +130,15 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     string.Empty, "Index", "Home", "http", "contoso.com", "hello=world", null, null))
                 .Returns(new TagBuilder("a"))
                 .Verifiable();
-            anchorTagHelper.Generator = generator.Object;
+            var anchorTagHelper = new AnchorTagHelper
+            {
+                Action = "Index",
+                Controller = "Home",
+                Fragment = "hello=world",
+                Generator = generator.Object,
+                Host = "contoso.com",
+                Protocol = "http",
+            };
 
             // Act & Assert
             await anchorTagHelper.ProcessAsync(context, output);
@@ -155,7 +155,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         [InlineData("Protocol")]
         [InlineData("Host")]
         [InlineData("Fragment")]
-        [InlineData("route-")]
+        [InlineData("asp-route-")]
         public async Task ProcessAsync_ThrowsIfHrefConflictsWithBoundAttributes(string propertyName)
         {
             // Arrange
@@ -167,19 +167,19 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     { "href", "http://www.contoso.com" }
                 },
                 content: string.Empty);
-
+            if (propertyName == "asp-route-")
-            if (propertyName == "route-")
             {
-                output.Attributes.Add("route-foo", "bar");
+                output.Attributes.Add("asp-route-foo", "bar");
             }
             else
             {
                 typeof(AnchorTagHelper).GetProperty(propertyName).SetValue(anchorTagHelper, "Home");
             }
 
-            var expectedErrorMessage = "Cannot determine an 'href' for <a>. An <a> with a specified 'href' must not " +
+            var expectedErrorMessage = "Cannot override the 'href' attribute for <a>. An <a> with a specified " +
-                                       "have attributes starting with 'route-' or an 'action', 'controller', " +
+                                       "'href' must not have attributes starting with 'asp-route-' or an " +
-                                       "'route', 'protocol', 'host', or 'fragment' attribute.";
+                                       "'asp-action', 'asp-controller', 'asp-route', 'asp-protocol', 'asp-host', or " +
+                                       "'asp-fragment' attribute.";
 
             // Act & Assert
             var ex = await Assert.ThrowsAsync<InvalidOperationException>(
@@ -196,15 +196,15 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Arrange
             var anchorTagHelper = new AnchorTagHelper
             {
-                Route = "Default"
+                Route = "Default",
             };
             typeof(AnchorTagHelper).GetProperty(propertyName).SetValue(anchorTagHelper, "Home");
             var output = new TagHelperOutput(
                 "a",
                 attributes: new Dictionary<string, string>(),
                 content: string.Empty);
-            var expectedErrorMessage = "Cannot determine an 'href' for <a>. An <a> with a " +
+            var expectedErrorMessage = "Cannot determine an 'href' attribute for <a>. An <a> with a specified " +
-                                       "specified 'route' must not have an 'action' or 'controller' attribute.";
+                "'asp-route' must not have an 'asp-action' or 'asp-controller' attribute.";
 
             // Act & Assert
             var ex = await Assert.ThrowsAsync<InvalidOperationException>(

test/Microsoft.AspNet.Mvc.TagHelpers.Test/FormTagHelperTest.cs

@@ -23,29 +23,22 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Arrange
             var expectedTagName = "not-form";
             var metadataProvider = new DataAnnotationsModelMetadataProvider();
-            var formTagHelper = new FormTagHelper
-            {
-                Action = "index",
-                Controller = "home",
-                Method = "post",
-                AntiForgery = true
-            };
             var tagHelperContext = new TagHelperContext(
                 allAttributes: new Dictionary<string, object>
                 {
                     { "id", "myform" },
-                    { "route-foo", "bar" },
+                    { "asp-route-foo", "bar" },
-                    { "action", "index" },
+                    { "asp-action", "index" },
-                    { "controller", "home" },
+                    { "asp-controller", "home" },
                     { "method", "post" },
-                    { "anti-forgery", true }
+                    { "asp-anti-forgery", true }
                 });
             var output = new TagHelperOutput(
                 expectedTagName,
                 attributes: new Dictionary<string, string>
                 {
                     { "id", "myform" },
-                    { "route-foo", "bar" },
+                    { "asp-route-foo", "bar" },
                 },
                 content: "Something");
             var urlHelper = new Mock<IUrlHelper>();
@@ -64,8 +57,15 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                                                                    metadataProvider: metadataProvider);
             var expectedContent = "Something" + htmlGenerator.GenerateAntiForgery(viewContext)
                                                              .ToString(TagRenderMode.SelfClosing);
-            formTagHelper.ViewContext = viewContext;
+            var formTagHelper = new FormTagHelper
-            formTagHelper.Generator = htmlGenerator;
+            {
+                Action = "index",
+                AntiForgery = true,
+                Controller = "home",
+                Generator = htmlGenerator,
+                Method = "post",
+                ViewContext = viewContext,
+            };
 
             // Act
             await formTagHelper.ProcessAsync(tagHelperContext, output);
@@ -90,11 +90,6 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         {
             // Arrange
             var viewContext = CreateViewContext();
-            var formTagHelper = new FormTagHelper
-            {
-                Action = "Index",
-                AntiForgery = antiForgery
-            };
             var context = new TagHelperContext(
                 allAttributes: new Dictionary<string, object>());
             var output = new TagHelperOutput(
@@ -114,8 +109,13 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             generator.Setup(mock => mock.GenerateAntiForgery(viewContext))
                      .Returns(new TagBuilder("input"));
-            formTagHelper.ViewContext = viewContext;
+            var formTagHelper = new FormTagHelper
-            formTagHelper.Generator = generator.Object;
+            {
+                Action = "Index",
+                AntiForgery = antiForgery,
+                Generator = generator.Object,
+                ViewContext = viewContext,
+            };
 
             // Act
             await formTagHelper.ProcessAsync(context, output);
@@ -131,20 +131,15 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         {
             // Arrange
             var testViewContext = CreateViewContext();
-            var formTagHelper = new FormTagHelper
-            {
-                Action = "Index",
-                AntiForgery = false
-            };
             var context = new TagHelperContext(
                 allAttributes: new Dictionary<string, object>());
-            var expectedAttribute = new KeyValuePair<string, string>("ROUTEE-NotRoute", "something");
+            var expectedAttribute = new KeyValuePair<string, string>("asp-ROUTEE-NotRoute", "something");
             var output = new TagHelperOutput(
                 "form",
                 attributes: new Dictionary<string, string>()
                 {
-                    { "route-val", "hello" },
+                    { "asp-route-val", "hello" },
-                    { "roUte--Foo", "bar" }
+                    { "asp-roUte--Foo", "bar" }
                 },
                 content: string.Empty);
             output.Attributes.Add(expectedAttribute);
@@ -174,8 +169,13 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                     })
                 .Returns(new TagBuilder("form"))
                 .Verifiable();
-            formTagHelper.ViewContext = testViewContext;
+            var formTagHelper = new FormTagHelper
-            formTagHelper.Generator = generator.Object;
+            {
+                Action = "Index",
+                AntiForgery = false,
+                Generator = generator.Object,
+                ViewContext = testViewContext,
+            };
 
             // Act & Assert
             await formTagHelper.ProcessAsync(context, output);
@@ -192,13 +192,6 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         {
             // Arrange
             var viewContext = CreateViewContext();
-            var formTagHelper = new FormTagHelper
-            {
-                Action = "Index",
-                Controller = "Home",
-                Method = "POST",
-                AntiForgery = false
-            };
             var context = new TagHelperContext(
                 allAttributes: new Dictionary<string, object>());
             var output = new TagHelperOutput(
@@ -210,8 +203,15 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 .Setup(mock => mock.GenerateForm(viewContext, "Index", "Home", null, "POST", null))
                 .Returns(new TagBuilder("form"))
                 .Verifiable();
-            formTagHelper.ViewContext = viewContext;
+            var formTagHelper = new FormTagHelper
-            formTagHelper.Generator = generator.Object;
+            {
+                Action = "Index",
+                AntiForgery = false,
+                Controller = "Home",
+                Generator = generator.Object,
+                Method = "POST",
+                ViewContext = viewContext,
+            };
 
             // Act & Assert
             await formTagHelper.ProcessAsync(context, output);
@@ -222,22 +222,26 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Empty(output.Content);
         }
 
-        [Fact]
+        [Theory]
-        public async Task ProcessAsync_RestoresBoundAttributesIfActionIsURL()
+        [InlineData("my-action")]
+        [InlineData("http://www.contoso.com")]
+        [InlineData("my/action")]
+        public async Task ProcessAsync_RestoresBoundAttributesIfActionIsSpecified(string htmlAction)
         {
             // Arrange
             var formTagHelper = new FormTagHelper
             {
-                Action = "http://www.contoso.com",
                 Method = "POST"
             };
             var output = new TagHelperOutput("form",
-                                             attributes: new Dictionary<string, string>(),
+                                             attributes: new Dictionary<string, string>
+                                             {
+                                                 { "aCTiON", htmlAction },
+                                             },
                                              content: string.Empty);
             var context = new TagHelperContext(
                 allAttributes: new Dictionary<string, object>()
                 {
-                    { "aCTiON", "http://www.contoso.com" },
                     { "METhod", "POST" }
                 });
 
@@ -248,7 +252,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("form", output.TagName);
             Assert.Equal(2, output.Attributes.Count);
             var attribute = Assert.Single(output.Attributes, kvp => kvp.Key.Equals("aCTiON"));
-            Assert.Equal("http://www.contoso.com", attribute.Value);
+            Assert.Equal(htmlAction, attribute.Value);
             attribute = Assert.Single(output.Attributes, kvp => kvp.Key.Equals("METhod"));
             Assert.Equal("POST", attribute.Value);
             Assert.Empty(output.Content);
@@ -258,7 +262,9 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         [InlineData(true, "<input />")]
         [InlineData(false, "")]
         [InlineData(null, "")]
-        public async Task ProcessAsync_SupportsAntiForgeryIfActionIsURL(bool? antiForgery, string expectedContent)
+        public async Task ProcessAsync_SupportsAntiForgeryIfActionIsSpecified(
+            bool? antiForgery,
+            string expectedContent)
         {
             // Arrange
             var viewContext = CreateViewContext();
@@ -267,20 +273,18 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                      .Returns(new TagBuilder("input"));
             var formTagHelper = new FormTagHelper
             {
-                Action = "http://www.contoso.com",
                 AntiForgery = antiForgery,
+                Generator = generator.Object,
+                ViewContext = viewContext,
             };
-            formTagHelper.ViewContext = viewContext;
-            formTagHelper.Generator = generator.Object;
 
             var output = new TagHelperOutput("form",
-                                             attributes: new Dictionary<string, string>(),
+                                             attributes: new Dictionary<string, string>
+                                             {
+                                                 { "aCTiON", "my-action" },
+                                             },
                                              content: string.Empty);
-            var context = new TagHelperContext(
+            var context = new TagHelperContext(allAttributes: new Dictionary<string, object>());
-                allAttributes: new Dictionary<string, object>()
-                {
-                    { "aCTiON", "http://www.contoso.com" }
-                });
 
             // Act
             await formTagHelper.ProcessAsync(context, output);
@@ -288,52 +292,40 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Assert
             Assert.Equal("form", output.TagName);
             var attribute = Assert.Single(output.Attributes);
-            Assert.Equal(new KeyValuePair<string, string>("aCTiON", "http://www.contoso.com"), attribute);
+            Assert.Equal(new KeyValuePair<string, string>("aCTiON", "my-action"), attribute);
             Assert.Equal(expectedContent, output.Content);
         }
 
-        [Fact]
+        [Theory]
-        public async Task ProcessAsync_ThrowsIfActionIsUrlWithSpecifiedController()
+        [InlineData("Action")]
+        [InlineData("Controller")]
+        [InlineData("asp-route-")]
+        public async Task ProcessAsync_ThrowsIfActionConflictsWithBoundAttributes(string propertyName)
         {
             // Arrange
             var formTagHelper = new FormTagHelper
             {
-                Action = "http://www.contoso.com",
-                Controller = "Home",
                 Method = "POST"
             };
-            var expectedErrorMessage = "Cannot determine an 'action' for <form>. A <form> with a URL-based 'action' " +
-                                       "must not have attributes starting with 'route-' or a 'controller' attribute.";
-            var tagHelperOutput = new TagHelperOutput(
-                "form",
-                attributes: new Dictionary<string, string>(),
-                content: string.Empty);
-
-            // Act & Assert
-            var ex = await Assert.ThrowsAsync<InvalidOperationException>(
-                () => formTagHelper.ProcessAsync(context: null, output: tagHelperOutput));
-
-            Assert.Equal(expectedErrorMessage, ex.Message);
-        }
-
-        [Fact]
-        public async Task ProcessAsync_ThrowsIfActionIsUrlWithSpecifiedRoutes()
-        {
-            // Arrange
-            var formTagHelper = new FormTagHelper
-            {
-                Action = "http://www.contoso.com",
-                Method = "POST"
-            };
-            var expectedErrorMessage = "Cannot determine an 'action' for <form>. A <form> with a URL-based 'action' " +
-                                       "must not have attributes starting with 'route-' or a 'controller' attribute.";
             var tagHelperOutput = new TagHelperOutput(
                 "form",
                 attributes: new Dictionary<string, string>
                 {
-                    { "route-foo", "bar" }
+                    { "action", "my-action" },
                 },
                 content: string.Empty);
+            if (propertyName == "asp-route-")
+            {
+                tagHelperOutput.Attributes.Add("asp-route-foo", "bar");
+            }
+            else
+            {
+                typeof(FormTagHelper).GetProperty(propertyName).SetValue(formTagHelper, "Home");
+            }
+
+            var expectedErrorMessage = "Cannot override the 'action' attribute for <form>. A <form> with a specified " +
+                                       "'action' must not have attributes starting with 'asp-route-' or an " +
+                                       "'asp-action' or 'asp-controller' attribute.";
 
             // Act & Assert
             var ex = await Assert.ThrowsAsync<InvalidOperationException>(

test/Microsoft.AspNet.Mvc.TagHelpers.Test/InputTagHelperTest.cs

@@ -552,6 +552,30 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 expressionName: propertyName);
         }
 
+        [Fact]
+        public async Task ProcessAsync_Throws_IfForNotBoundButFormatIs()
+        {
+            // Arrange
+            var contextAttributes = new Dictionary<string, object>();
+            var originalAttributes = new Dictionary<string, string>();
+            var content = "original content";
+            var expectedTagName = "select";
+            var expectedMessage = "Unable to format without a 'asp-for' expression for <input>. 'asp-format' must " +
+                "be null if 'asp-for' is null.";
+
+            var tagHelperContext = new TagHelperContext(contextAttributes);
+            var output = new TagHelperOutput(expectedTagName, originalAttributes, content);
+            var tagHelper = new InputTagHelper
+            {
+                Format = "{0}",
+            };
+
+            // Act & Assert
+            var exception = await Assert.ThrowsAsync<InvalidOperationException>(
+                () => tagHelper.ProcessAsync(tagHelperContext, output));
+            Assert.Equal(expectedMessage, exception.Message);
+        }
+
         private static InputTagHelper GetTagHelper(
             IHtmlGenerator htmlGenerator,
             object container,

test/Microsoft.AspNet.Mvc.TagHelpers.Test/SelectTagHelperTest.cs

@@ -469,7 +469,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var originalAttributes = new Dictionary<string, string>();
             var content = "original content";
             var expectedTagName = "select";
-            var expectedMessage = "Cannot determine body for <select>. 'items' must be null if 'for' is null.";
+            var expectedMessage = "Cannot determine body for <select>. 'asp-items' must be null if 'asp-for' is null.";
 
             var tagHelperContext = new TagHelperContext(contextAttributes);
             var output = new TagHelperOutput(expectedTagName, originalAttributes, content);

test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationSummaryTagHelperTest.cs

@@ -253,8 +253,8 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                 attributes: new Dictionary<string, string>(),
                 content: "Content of validation message");
             var expectedViewContext = CreateViewContext();
-            var expectedMessage = "Cannot parse 'validation-summary' value 'Hello World' for <div>. Acceptable values " +
+            var expectedMessage = "Cannot parse 'asp-validation-summary' value 'Hello World' for <div>. Acceptable " +
-                                  "are 'All', 'ModelOnly' and 'None'.";
+                                  "values are 'All', 'ModelOnly' and 'None'.";
 
             // Act
             var ex = await Assert.ThrowsAsync<InvalidOperationException>(