Added fragment to FormActionTagHelper and FormActionTagHelper

Addresses #4917

src/Microsoft.AspNetCore.Mvc.TagHelpers/FormActionTagHelper.cs

@@ -18,18 +18,21 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
     [HtmlTargetElement("button", Attributes = ActionAttributeName)]
     [HtmlTargetElement("button", Attributes = ControllerAttributeName)]
     [HtmlTargetElement("button", Attributes = AreaAttributeName)]
+    [HtmlTargetElement("button", Attributes = FragmentAttributeName)]
     [HtmlTargetElement("button", Attributes = RouteAttributeName)]
     [HtmlTargetElement("button", Attributes = RouteValuesDictionaryName)]
     [HtmlTargetElement("button", Attributes = RouteValuesPrefix + "*")]
     [HtmlTargetElement("input", Attributes = ImageActionAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
     [HtmlTargetElement("input", Attributes = ImageControllerAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
     [HtmlTargetElement("input", Attributes = ImageAreaAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
+    [HtmlTargetElement("input", Attributes = ImageFragmentAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
     [HtmlTargetElement("input", Attributes = ImageRouteAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
     [HtmlTargetElement("input", Attributes = ImageRouteValuesDictionarySelector, TagStructure = TagStructure.WithoutEndTag)]
     [HtmlTargetElement("input", Attributes = ImageRouteValuesSelector, TagStructure = TagStructure.WithoutEndTag)]
     [HtmlTargetElement("input", Attributes = SubmitActionAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
     [HtmlTargetElement("input", Attributes = SubmitControllerAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
     [HtmlTargetElement("input", Attributes = SubmitAreaAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
+    [HtmlTargetElement("input", Attributes = SubmitFragmentAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
     [HtmlTargetElement("input", Attributes = SubmitRouteAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
     [HtmlTargetElement("input", Attributes = SubmitRouteValuesDictionarySelector, TagStructure = TagStructure.WithoutEndTag)]
     [HtmlTargetElement("input", Attributes = SubmitRouteValuesSelector, TagStructure = TagStructure.WithoutEndTag)]
@@ -38,6 +41,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         private const string ActionAttributeName = "asp-action";
         private const string AreaAttributeName = "asp-area";
         private const string ControllerAttributeName = "asp-controller";
+        private const string FragmentAttributeName = "asp-fragment";
         private const string RouteAttributeName = "asp-route";
         private const string RouteValuesDictionaryName = "asp-all-route-data";
         private const string RouteValuesPrefix = "asp-route-";
@@ -46,6 +50,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         private const string ImageTypeSelector = "[type=image], ";
         private const string ImageActionAttributeSelector = ImageTypeSelector + ActionAttributeName;
         private const string ImageAreaAttributeSelector = ImageTypeSelector + AreaAttributeName;
+        private const string ImageFragmentAttributeSelector = ImageTypeSelector + FragmentAttributeName;
         private const string ImageControllerAttributeSelector = ImageTypeSelector + ControllerAttributeName;
         private const string ImageRouteAttributeSelector = ImageTypeSelector + RouteAttributeName;
         private const string ImageRouteValuesDictionarySelector = ImageTypeSelector + RouteValuesDictionaryName;
@@ -54,6 +59,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         private const string SubmitTypeSelector = "[type=submit], ";
         private const string SubmitActionAttributeSelector = SubmitTypeSelector + ActionAttributeName;
         private const string SubmitAreaAttributeSelector = SubmitTypeSelector + AreaAttributeName;
+        private const string SubmitFragmentAttributeSelector = SubmitTypeSelector + FragmentAttributeName;
         private const string SubmitControllerAttributeSelector = SubmitTypeSelector + ControllerAttributeName;
         private const string SubmitRouteAttributeSelector = SubmitTypeSelector + RouteAttributeName;
         private const string SubmitRouteValuesDictionarySelector = SubmitTypeSelector + RouteValuesDictionaryName;
@@ -100,6 +106,12 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         [HtmlAttributeName(AreaAttributeName)]
         public string Area { get; set; }
 
+        /// <summary>
+        /// Gets or sets the URL fragment.
+        /// </summary>
+        [HtmlAttributeName(FragmentAttributeName)]
+        public string Fragment { get; set; }
+
         /// <summary>
         /// Name of the route.
         /// </summary>
@@ -134,7 +146,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         /// <remarks>Does nothing if user provides an <c>formaction</c> attribute.</remarks>
         /// <exception cref="InvalidOperationException">
         /// Thrown if <c>formaction</c> attribute is provided and <see cref="Action"/>, <see cref="Controller"/>,
-        /// or <see cref="Route"/> are non-<c>null</c> or if the user provided <c>asp-route-*</c> attributes.
+        /// <see cref="Fragment"/> 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>
@@ -156,6 +168,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                 if (Action != null ||
                     Controller != null ||
                     Area != null ||
+                    Fragment != null ||
                     Route != null ||
                     (_routeValues != null && _routeValues.Count > 0))
                 {
@@ -167,6 +180,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                             ActionAttributeName,
                             ControllerAttributeName,
                             AreaAttributeName,
+                            FragmentAttributeName,
                             RouteAttributeName,
                             RouteValuesPrefix,
                             FormAction));
@@ -194,7 +208,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                 if (Route == null)
                 {
                     var urlHelper = UrlHelperFactory.GetUrlHelper(ViewContext);
-                    var url = urlHelper.Action(Action, Controller, routeValues);
+                    var url = urlHelper.Action(Action, Controller, routeValues, protocol: null, host: null, fragment: Fragment);
                     output.Attributes.SetAttribute(FormAction, url);
                 }
                 else if (Action != null || Controller != null)
@@ -206,12 +220,13 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                             RouteAttributeName,
                             ActionAttributeName,
                             ControllerAttributeName,
-                            FormAction));
+                            FormAction,
+                            FragmentAttributeName));
                 }
                 else
                 {
                     var urlHelper = UrlHelperFactory.GetUrlHelper(ViewContext);
-                    var url = urlHelper.RouteUrl(Route, routeValues);
+                    var url = urlHelper.RouteUrl(Route, routeValues, protocol: null, host: null, fragment: Fragment);
                     output.Attributes.SetAttribute(FormAction, url);
                 }
             }

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

@@ -16,6 +16,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
     [HtmlTargetElement("form", Attributes = ActionAttributeName)]
     [HtmlTargetElement("form", Attributes = AntiforgeryAttributeName)]
     [HtmlTargetElement("form", Attributes = AreaAttributeName)]
+    [HtmlTargetElement("form", Attributes = FragmentAttributeName)]
     [HtmlTargetElement("form", Attributes = ControllerAttributeName)]
     [HtmlTargetElement("form", Attributes = RouteAttributeName)]
     [HtmlTargetElement("form", Attributes = RouteValuesDictionaryName)]
@@ -25,6 +26,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         private const string ActionAttributeName = "asp-action";
         private const string AntiforgeryAttributeName = "asp-antiforgery";
         private const string AreaAttributeName = "asp-area";
+        private const string FragmentAttributeName = "asp-fragment";
         private const string ControllerAttributeName = "asp-controller";
         private const string RouteAttributeName = "asp-route";
         private const string RouteValuesDictionaryName = "asp-all-route-data";
@@ -78,6 +80,12 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         [HtmlAttributeName(AntiforgeryAttributeName)]
         public bool? Antiforgery { get; set; }
 
+        /// <summary>
+        /// Gets or sets the URL fragment.
+        /// </summary>
+        [HtmlAttributeName(FragmentAttributeName)]
+        public string Fragment { get; set; }
+
         /// <summary>
         /// Name of the route.
         /// </summary>
@@ -121,7 +129,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         /// <c>false</c>.
         /// </remarks>
         /// <exception cref="InvalidOperationException">
-        /// Thrown if <c>action</c> attribute is provided and <see cref="Action"/> or <see cref="Controller"/> are
+        /// Thrown if <c>action</c> attribute is provided and <see cref="Action"/>, <see cref="Controller"/> or <see cref="Fragment"/> are
         /// non-<c>null</c> or if the user provided <c>asp-route-*</c> attributes.
         /// </exception>
         public override void Process(TagHelperContext context, TagHelperOutput output)
@@ -148,6 +156,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                 if (Action != null ||
                     Controller != null ||
                     Area != null ||
+                    Fragment != null ||
                     Route != null ||
                     (_routeValues != null && _routeValues.Count > 0))
                 {
@@ -158,6 +167,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                             HtmlActionAttributeName,
                             ActionAttributeName,
                             ControllerAttributeName,
+                            FragmentAttributeName,
                             AreaAttributeName,
                             RouteAttributeName,
                             RouteValuesPrefix));
@@ -198,6 +208,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                         ViewContext,
                         Action,
                         Controller,
+                        Fragment,
                         routeValues,
                         method: null,
                         htmlAttributes: null);
@@ -211,7 +222,8 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                             RouteAttributeName,
                             ActionAttributeName,
                             ControllerAttributeName,
-                            HtmlActionAttributeName));
+                            HtmlActionAttributeName,
+                            FragmentAttributeName));
                 }
                 else
                 {
@@ -219,6 +231,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                         ViewContext,
                         Route,
                         routeValues,
+                        Fragment,
                         method: null,
                         htmlAttributes: null);
                 }

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

@@ -43,7 +43,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         }
 
         /// <summary>
-        /// Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{6}' or an '{2}' or '{3}' or '{4}' or '{5}' attribute.
+        /// Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{7}' or an '{2}', '{3}', '{4}', '{5}', or '{6}' attribute.
         /// </summary>
         internal static string FormTagHelper_CannotOverrideAction
         {
@@ -51,11 +51,11 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         }
 
         /// <summary>
-        /// Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{6}' or an '{2}' or '{3}' or '{4}' or '{5}' attribute.
+        /// Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{7}' or an '{2}', '{3}', '{4}', '{5}', or '{6}' attribute.
         /// </summary>
-        internal static string FormatFormTagHelper_CannotOverrideAction(object p0, object p1, object p2, object p3, object p4, object p5, object p6)
+        internal static string FormatFormTagHelper_CannotOverrideAction(object p0, object p1, object p2, object p3, object p4, object p5, object p6, object p7)
         {
-            return string.Format(CultureInfo.CurrentCulture, GetString("FormTagHelper_CannotOverrideAction"), p0, p1, p2, p3, p4, p5, p6);
+            return string.Format(CultureInfo.CurrentCulture, GetString("FormTagHelper_CannotOverrideAction"), p0, p1, p2, p3, p4, p5, p6, p7);
         }
 
         /// <summary>
@@ -147,11 +147,11 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         }
 
         /// <summary>
-        /// Cannot determine an '{4}' attribute for {0}. A {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.
+        /// Cannot determine an '{4}' attribute for {0}. A {0} with a specified '{1}' must not have an '{2}', '{3}', or '{5}' attribute.
         /// </summary>
-        internal static string FormatFormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified(object p0, object p1, object p2, object p3, object p4)
+        internal static string FormatFormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified(object p0, object p1, object p2, object p3, object p4, object p5)
         {
-            return string.Format(CultureInfo.CurrentCulture, GetString("FormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified"), p0, p1, p2, p3, p4);
+            return string.Format(CultureInfo.CurrentCulture, GetString("FormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified"), p0, p1, p2, p3, p4, p5);
         }
 
         /// <summary>
@@ -179,11 +179,11 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         }
 
         /// <summary>
-        /// Cannot override the '{6}' attribute for &lt;{0}&gt;. &lt;{0}&gt; elements with a specified '{6}' must not have attributes starting with '{5}' or an '{1}', '{2}', '{3}', or '{4}' attribute.
+        /// Cannot override the '{6}' attribute for &lt;{0}&gt;. &lt;{0}&gt; elements with a specified '{7}' must not have attributes starting with '{6}' or an '{1}', '{2}', '{3}', '{4}', or '{5}' attribute.
         /// </summary>
-        internal static string FormatFormActionTagHelper_CannotOverrideFormAction(object p0, object p1, object p2, object p3, object p4, object p5, object p6)
+        internal static string FormatFormActionTagHelper_CannotOverrideFormAction(object p0, object p1, object p2, object p3, object p4, object p5, object p6, object p7)
         {
-            return string.Format(CultureInfo.CurrentCulture, GetString("FormActionTagHelper_CannotOverrideFormAction"), p0, p1, p2, p3, p4, p5, p6);
+            return string.Format(CultureInfo.CurrentCulture, GetString("FormActionTagHelper_CannotOverrideFormAction"), p0, p1, p2, p3, p4, p5, p6, p7);
         }
 
         /// <summary>
@@ -195,11 +195,11 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         }
 
         /// <summary>
-        /// Cannot determine a '{4}' attribute for &lt;{0}&gt;. &lt;{0}&gt; elements with a specified '{1}' must not have an '{2}' or '{3}' attribute.
+        /// Cannot determine a '{4}' attribute for &lt;{0}&gt;. &lt;{0}&gt; elements with a specified '{1}' must not have an '{2}', '{3}', or '{5}' attribute.
         /// </summary>
-        internal static string FormatFormActionTagHelper_CannotDetermineFormActionRouteActionOrControllerSpecified(object p0, object p1, object p2, object p3, object p4)
+        internal static string FormatFormActionTagHelper_CannotDetermineFormActionRouteActionOrControllerSpecified(object p0, object p1, object p2, object p3, object p4, object p5)
         {
-            return string.Format(CultureInfo.CurrentCulture, GetString("FormActionTagHelper_CannotDetermineFormActionRouteActionOrControllerSpecified"), p0, p1, p2, p3, p4);
+            return string.Format(CultureInfo.CurrentCulture, GetString("FormActionTagHelper_CannotDetermineFormActionRouteActionOrControllerSpecified"), p0, p1, p2, p3, p4, p5);
         }
 
         private static string GetString(string name, params string[] formatterNames)

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

@@ -124,7 +124,7 @@
     <value>Cannot override the '{9}' attribute for {0}. An {0} with a specified '{9}' must not have attributes starting with '{8}' or an '{1}', '{2}', '{3}', '{4}', '{5}', '{6}', or '{7}' 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 '{6}' or an '{2}' or '{3}' or '{4}' or '{5}' attribute.</value>
+    <value>Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{7}' or an '{2}', '{3}', '{4}', '{5}', or '{6}' 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>
@@ -142,15 +142,15 @@
     <value>The attribute '{0}' does not exist in the {1}.</value>
   </data>
   <data name="FormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified" xml:space="preserve">
-    <value>Cannot determine an '{4}' attribute for {0}. A {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.</value>
+    <value>Cannot determine an '{4}' attribute for {0}. A {0} with a specified '{1}' must not have an '{2}', '{3}', or '{5}' attribute.</value>
   </data>
   <data name="PropertyOfTypeCannotBeNull" xml:space="preserve">
     <value>The '{0}' property of '{1}' must not be null.</value>
   </data>
   <data name="FormActionTagHelper_CannotOverrideFormAction" xml:space="preserve">
-    <value>Cannot override the '{6}' attribute for &lt;{0}&gt;. &lt;{0}&gt; elements with a specified '{6}' must not have attributes starting with '{5}' or an '{1}', '{2}', '{3}', or '{4}' attribute.</value>
+    <value>Cannot override the '{7}' attribute for &lt;{0}&gt;. &lt;{0}&gt; elements with a specified '{7}' must not have attributes starting with '{6}' or an '{1}', '{2}', '{3}', '{4}', or '{5}' attribute.</value>
   </data>
   <data name="FormActionTagHelper_CannotDetermineFormActionRouteActionOrControllerSpecified" xml:space="preserve">
-    <value>Cannot determine a '{4}' attribute for &lt;{0}&gt;. &lt;{0}&gt; elements with a specified '{1}' must not have an '{2}' or '{3}' attribute.</value>
+    <value>Cannot determine a '{4}' attribute for &lt;{0}&gt;. &lt;{0}&gt; elements with a specified '{1}' must not have an '{2}', '{3}', or '{5}' attribute.</value>
   </data>
 </root>

src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewFeatures/DefaultHtmlGeneratorExtensions.cs

@@ -0,0 +1,51 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Mvc.Rendering;
+
+namespace Microsoft.AspNetCore.Mvc.ViewFeatures
+{
+    public static class DefaultHtmlGeneratorExtensions
+    {
+        public static TagBuilder GenerateForm(
+            this IHtmlGenerator generator,
+            ViewContext viewContext,
+            string actionName,
+            string controllerName,
+            string fragment,
+            object routeValues,
+            string method,
+            object htmlAttributes)
+        {
+            var tagBuilder = generator.GenerateForm(viewContext, actionName, controllerName, routeValues, method, htmlAttributes);
+
+            // Append the fragment to action
+            if (fragment != null)
+            {
+                tagBuilder.Attributes["action"] += "#" + fragment;
+            }
+
+            return tagBuilder;
+        }
+
+        public static TagBuilder GenerateRouteForm(
+            this IHtmlGenerator generator,
+            ViewContext viewContext,
+            string routeName,
+            object routeValues,
+            string fragment,
+            string method,
+            object htmlAttributes)
+        {
+            var tagBuilder = generator.GenerateRouteForm(viewContext, routeName, routeValues, method, htmlAttributes);
+
+            // Append the fragment to action
+            if (fragment != null)
+            {
+                tagBuilder.Attributes["action"] += "#" + fragment;
+            }
+
+            return tagBuilder;
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.TagHelpers.Test/FormActionTagHelperTest.cs

@@ -221,7 +221,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                 {
                     Assert.Equal("delete", param.Action, StringComparer.Ordinal);
                     Assert.Equal("books", param.Controller, StringComparer.Ordinal);
-                    Assert.Null(param.Fragment);
+                    Assert.Equal("test", param.Fragment, StringComparer.Ordinal);
                     Assert.Null(param.Host);
                     Assert.Null(param.Protocol);
                     Assert.Equal<KeyValuePair<string, object>>(expectedRouteValues, param.Values as RouteValueDictionary);
@@ -238,6 +238,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
             {
                 Action = "delete",
                 Controller = "books",
+                Fragment = "test",
                 RouteValues = routeValues,
                 ViewContext = viewContext,
             };
@@ -277,9 +278,9 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                 .Setup(mock => mock.RouteUrl(It.IsAny<UrlRouteContext>()))
                 .Callback<UrlRouteContext>(param =>
                 {
-                    Assert.Null(param.Fragment);
                     Assert.Null(param.Host);
                     Assert.Null(param.Protocol);
+                    Assert.Equal("test", param.Fragment, StringComparer.Ordinal);
                     Assert.Equal("Default", param.RouteName, StringComparer.Ordinal);
                     Assert.Equal<KeyValuePair<string, object>>(expectedRouteValues, param.Values as RouteValueDictionary);
                 })
@@ -294,6 +295,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
             var tagHelper = new FormActionTagHelper(urlHelperFactory.Object)
             {
                 Route = "Default",
+                Fragment = "test",
                 RouteValues = routeValues,
                 ViewContext = viewContext,
             };
@@ -467,7 +469,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
 
             var expectedErrorMessage = $"Cannot override the 'formaction' attribute for <{tagName}>. <{tagName}> " +
                 "elements with a specified 'formaction' must not have attributes starting with 'asp-route-' or an " +
-                "'asp-action', 'asp-controller', 'asp-area', or 'asp-route' attribute.";
+                "'asp-action', 'asp-controller', 'asp-area', 'asp-fragment', or 'asp-route' attribute.";
 
             var context = new TagHelperContext(
                 allAttributes: new TagHelperAttributeList(
@@ -502,7 +504,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                 attributes: new TagHelperAttributeList(),
                 getChildContentAsync: (useCachedResult, encoder) => Task.FromResult<TagHelperContent>(null));
             var expectedErrorMessage = $"Cannot determine a 'formaction' attribute for <{tagName}>. <{tagName}> " +
-                "elements with a specified 'asp-route' must not have an 'asp-action' or 'asp-controller' attribute.";
+                "elements with a specified 'asp-route' must not have an 'asp-action', 'asp-controller', or 'asp-fragment' attribute.";
 
             var context = new TagHelperContext(
                 allAttributes: new TagHelperAttributeList(

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

@@ -284,6 +284,72 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
             Assert.Empty(output.PostContent.GetContent());
         }
 
+        [Fact]
+        public async Task ProcessAsync_AspFragmentAddsFragmentToAction()
+        {
+            // Arrange
+            var expectedTagName = "form";
+            var metadataProvider = new TestModelMetadataProvider();
+            var tagHelperContext = new TagHelperContext(
+                allAttributes: new TagHelperAttributeList
+                {
+                    { "id", "myform" },
+                    { "asp-route-name", "value" },
+                    { "asp-action", "index" },
+                    { "asp-controller", "home" },
+                    { "asp-fragment", "test" },
+                    { "method", "post" },
+                    { "asp-antiforgery", true }
+                },
+                items: new Dictionary<object, object>(),
+                uniqueId: "test");
+
+            var output = new TagHelperOutput(
+                expectedTagName,
+                attributes: new TagHelperAttributeList
+                {
+                    { "id", "myform" },
+                },
+                getChildContentAsync: (useCachedResult, encoder) =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
+
+            var urlHelper = new Mock<IUrlHelper>();
+            urlHelper
+                .Setup(mock => mock.Action(It.IsAny<UrlActionContext>())).Returns("home/index");
+
+            var htmlGenerator = new TestableHtmlGenerator(metadataProvider, urlHelper.Object);
+            var viewContext = TestableHtmlGenerator.GetViewContext(
+                model: null,
+                htmlGenerator: htmlGenerator,
+                metadataProvider: metadataProvider);
+
+            var formTagHelper = new FormTagHelper(htmlGenerator)
+            {
+                Action = "index",
+                Antiforgery = true,
+                Controller = "home",
+                Fragment = "test",
+                ViewContext = viewContext,
+                RouteValues =
+                {
+                    { "name", "value" },
+                },
+            };
+
+            // Act
+            await formTagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+
+            Assert.Equal("form", output.TagName);
+            Assert.Equal(TagMode.StartTagAndEndTag, output.TagMode);
+            var attribute = Assert.Single(output.Attributes, attr => attr.Name.Equals("action"));
+            Assert.Equal("home/index#test", attribute.Value);
+        }
+
         [Fact]
         public async Task ProcessAsync_AspAreaAddsAreaToRouteValues()
         {
@@ -585,7 +651,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
 
             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' or 'asp-area' or 'asp-route' attribute.";
+                                       "'asp-action', 'asp-controller', 'asp-fragment', 'asp-area', or 'asp-route' attribute.";
 
             var context = new TagHelperContext(
                 allAttributes: new TagHelperAttributeList(
@@ -616,7 +682,7 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
                 attributes: new TagHelperAttributeList(),
                 getChildContentAsync: (useCachedResult, encoder) => Task.FromResult<TagHelperContent>(null));
             var expectedErrorMessage = "Cannot determine an 'action' attribute for <form>. A <form> with a specified " +
-                "'asp-route' must not have an 'asp-action' or 'asp-controller' attribute.";
+                "'asp-route' must not have an 'asp-action', 'asp-controller', or 'asp-fragment' attribute.";
 
             var context = new TagHelperContext(
                 allAttributes: new TagHelperAttributeList(