diff --git a/samples/TagHelperSample.Web/Views/Home/Create.cshtml b/samples/TagHelperSample.Web/Views/Home/Create.cshtml
index 96054bb801..e7bee3837f 100644
--- a/samples/TagHelperSample.Web/Views/Home/Create.cshtml
+++ b/samples/TagHelperSample.Web/Views/Home/Create.cshtml
@@ -14,13 +14,14 @@
     <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 *@
-        @* helper does nothing if model is valid and (client-side validation is disabled or asp-validation-summary="ModelOnly") *@
+        @* helper does nothing if model is valid and (client-side validation is disabled or
+           asp-validation-summary="ValidationSummary.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 asp-validation-summary="All" style="color:blue" id="validation_day" class="form-group">
+        <div asp-validation-summary="ValidationSummary.All" style="color:blue" id="validation_day" class="form-group">
             <span style="color:red">This is my message</span>
         </div>
 
diff --git a/samples/TagHelperSample.Web/Views/Home/Edit.cshtml b/samples/TagHelperSample.Web/Views/Home/Edit.cshtml
index 97f277e011..1a49cf5d21 100644
--- a/samples/TagHelperSample.Web/Views/Home/Edit.cshtml
+++ b/samples/TagHelperSample.Web/Views/Home/Edit.cshtml
@@ -6,7 +6,7 @@
 
 <form>
     <div class="form-horizontal">
-        <div asp-validation-summary="All" />
+        <div asp-validation-summary="ValidationSummary.All" />
         <input type="hidden" asp-for="Id" />
 
         <div class="form-group">
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/Properties/Resources.Designer.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/Properties/Resources.Designer.cs
index f44a44fdb6..183d549f26 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/Properties/Resources.Designer.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/Properties/Resources.Designer.cs
@@ -154,6 +154,22 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             return string.Format(CultureInfo.CurrentCulture, GetString("TagHelpers_NoProvidedMetadata"), p0, p1, p2, p3);
         }
 
+        /// <summary>
+        /// The value of argument '{0}' ({1}) is invalid for Enum type '{2}'.
+        /// </summary>
+        internal static string InvalidEnumArgument
+        {
+            get { return GetString("InvalidEnumArgument"); }
+        }
+
+        /// <summary>
+        /// The value of argument '{0}' ({1}) is invalid for Enum type '{2}'.
+        /// </summary>
+        internal static string FormatInvalidEnumArgument(object p0, object p1, object p2)
+        {
+            return string.Format(CultureInfo.CurrentCulture, GetString("InvalidEnumArgument"), p0, p1, p2);
+        }
+
         private static string GetString(string name, params string[] formatterNames)
         {
             var value = _resourceManager.GetString(name);
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/Resources.resx b/src/Microsoft.AspNet.Mvc.TagHelpers/Resources.resx
index 75ccdd5b0b..43bda290f1 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/Resources.resx
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/Resources.resx
@@ -144,4 +144,7 @@
   <data name="TagHelpers_NoProvidedMetadata" xml:space="preserve">
     <value>The {2} was unable to provide metadata about '{1}' expression value '{3}' for {0}.</value>
   </data>
+  <data name="InvalidEnumArgument" xml:space="preserve">
+    <value>The value of argument '{0}' ({1}) is invalid for Enum type '{2}'.</value>
+  </data>
 </root>
\ No newline at end of file
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummary.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummary.cs
index 5b7c111c06..e56dcdc582 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummary.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummary.cs
@@ -1,7 +1,7 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-namespace Microsoft.AspNet.Mvc.TagHelpers
+namespace Microsoft.AspNet.Mvc
 {
     /// <summary>
     /// Acceptable validation summary rendering modes.
diff --git a/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummaryTagHelper.cs b/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummaryTagHelper.cs
index 3463b9acec..480945d9ff 100644
--- a/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummaryTagHelper.cs
+++ b/src/Microsoft.AspNet.Mvc.TagHelpers/ValidationSummaryTagHelper.cs
@@ -17,6 +17,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
     public class ValidationSummaryTagHelper : TagHelper
     {
         private const string ValidationSummaryAttributeName = "asp-validation-summary";
+        private ValidationSummary _validationSummary;
 
         // Protected to ensure subclasses are correctly activated. Internal for ease of use when testing.
         [Activate]
@@ -27,51 +28,60 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         protected internal IHtmlGenerator Generator { get; set; }
 
         /// <summary>
-        /// If <c>All</c> or <c>ModelOnly</c>, appends a validation summary. Acceptable values are defined by the
-        /// <see cref="ValidationSummary"/> enum.
+        /// If <see cref="ValidationSummary.All"/> or <see cref="ValidationSummary.ModelOnly"/>, appends a validation
+        /// summary. Otherwise (<see cref="ValidationSummary.None"/>, the default), this tag helper does nothing.
         /// </summary>
+        /// <exception cref="ArgumentException">
+        /// Thrown if setter is called with an undefined <see cref="ValidationSummary"/> value e.g.
+        /// <c>(ValidationSummary)23</c>.
+        /// </exception>
         [HtmlAttributeName(ValidationSummaryAttributeName)]
-        public string ValidationSummaryValue { get; set; }
+        public ValidationSummary ValidationSummary
+        {
+            get
+            {
+                return _validationSummary;
+            }
+            set
+            {
+                switch (value)
+                {
+                    case ValidationSummary.All:
+                    case ValidationSummary.ModelOnly:
+                    case ValidationSummary.None:
+                        _validationSummary = value;
+                        break;
+
+                    default:
+                        throw new ArgumentException(
+                            message: Resources.FormatInvalidEnumArgument(
+                                nameof(value),
+                                value,
+                                typeof(ValidationSummary).FullName),
+                            paramName: nameof(value));
+                }
+            }
+        }
 
         /// <inheritdoc />
-        /// <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>
+        /// <remarks>Does nothing if <see cref="ValidationSummary"/> is <see cref="ValidationSummary.None"/>.</remarks>
         public override void Process(TagHelperContext context, TagHelperOutput output)
         {
-            if (!string.IsNullOrEmpty(ValidationSummaryValue))
+            if (ValidationSummary == ValidationSummary.None)
             {
-                ValidationSummary validationSummaryValue;
-                if (!Enum.TryParse(ValidationSummaryValue, ignoreCase: true, result: out validationSummaryValue))
-                {
-                    throw new InvalidOperationException(
-                        Resources.FormatTagHelpers_InvalidValue_ThreeAcceptableValues(
-                            "<div>",
-                            ValidationSummaryAttributeName,
-                            ValidationSummaryValue,
-                            ValidationSummary.All,
-                            ValidationSummary.ModelOnly,
-                            ValidationSummary.None));
-                }
-                else if (validationSummaryValue == ValidationSummary.None)
-                {
-                    return;
-                }
+                return;
+            }
 
-                var validationModelErrorsOnly = validationSummaryValue == ValidationSummary.ModelOnly;
-                var tagBuilder = Generator.GenerateValidationSummary(
-                    ViewContext,
-                    excludePropertyErrors: validationModelErrorsOnly,
-                    message: null,
-                    headerTag: null,
-                    htmlAttributes: null);
-
-                if (tagBuilder != null)
-                {
-                    output.MergeAttributes(tagBuilder);
-                    output.Content += tagBuilder.InnerHtml;
-                }
+            var tagBuilder = Generator.GenerateValidationSummary(
+                ViewContext,
+                excludePropertyErrors: ValidationSummary == ValidationSummary.ModelOnly,
+                message: null,
+                headerTag: null,
+                htmlAttributes: null);
+            if (tagBuilder != null)
+            {
+                output.MergeAttributes(tagBuilder);
+                output.Content += tagBuilder.InnerHtml;
             }
         }
     }
diff --git a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationSummaryTagHelperTest.cs b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationSummaryTagHelperTest.cs
index bde704137a..bdad85e1a3 100644
--- a/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationSummaryTagHelperTest.cs
+++ b/test/Microsoft.AspNet.Mvc.TagHelpers.Test/ValidationSummaryTagHelperTest.cs
@@ -10,6 +10,7 @@ using Microsoft.AspNet.Mvc.ModelBinding;
 using Microsoft.AspNet.Mvc.Rendering;
 using Microsoft.AspNet.Razor.Runtime.TagHelpers;
 using Microsoft.AspNet.Routing;
+using Microsoft.AspNet.Testing;
 using Moq;
 using Xunit;
 
@@ -17,6 +18,17 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 {
     public class ValidationSummaryTagHelperTest
     {
+        public void Concstructor_IntializesProperties_AsExpected()
+        {
+            // Arrange & Act
+            var validationSummaryTagHelper = new ValidationSummaryTagHelper();
+
+            // Assert
+            Assert.Null(validationSummaryTagHelper.Generator);
+            Assert.Null(validationSummaryTagHelper.ViewContext);
+            Assert.Equal(ValidationSummary.None, validationSummaryTagHelper.ValidationSummary);
+        }
+
         [Fact]
         public async Task ProcessAsync_GeneratesExpectedOutput()
         {
@@ -25,7 +37,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var metadataProvider = new DataAnnotationsModelMetadataProvider();
             var validationSummaryTagHelper = new ValidationSummaryTagHelper
             {
-                ValidationSummaryValue = "All"
+                ValidationSummary = ValidationSummary.All,
             };
 
             var tagHelperContext = new TagHelperContext(new Dictionary<string, object>(), uniqueId: "test");
@@ -57,13 +69,17 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal(expectedTagName, output.TagName);
         }
 
-        [Fact]
-        public async Task ProcessAsync_CallsIntoGenerateValidationSummaryWithExpectedParameters()
+        [Theory]
+        [InlineData(ValidationSummary.All, false)]
+        [InlineData(ValidationSummary.ModelOnly, true)]
+        public async Task ProcessAsync_CallsIntoGenerateValidationSummaryWithExpectedParameters(
+            ValidationSummary validationSummary,
+            bool expectedExcludePropertyErrors)
         {
             // Arrange
             var validationSummaryTagHelper = new ValidationSummaryTagHelper
             {
-                ValidationSummaryValue = "ModelOnly",
+                ValidationSummary = validationSummary,
             };
             var output = new TagHelperOutput(
                 "div",
@@ -72,7 +88,12 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             var expectedViewContext = CreateViewContext();
             var generator = new Mock<IHtmlGenerator>();
             generator
-                .Setup(mock => mock.GenerateValidationSummary(expectedViewContext, true, null, null, null))
+                .Setup(mock => mock.GenerateValidationSummary(
+                    expectedViewContext,
+                    expectedExcludePropertyErrors,
+                    null,   // message
+                    null,   // headerTag
+                    null))  // htmlAttributes
                 .Returns(new TagBuilder("div"))
                 .Verifiable();
             validationSummaryTagHelper.ViewContext = expectedViewContext;
@@ -93,7 +114,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // Arrange
             var validationSummaryTagHelper = new ValidationSummaryTagHelper
             {
-                ValidationSummaryValue = "ModelOnly"
+                ValidationSummary = ValidationSummary.ModelOnly,
             };
             var output = new TagHelperOutput(
                 "div",
@@ -136,15 +157,13 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("Content of validation summaryNew HTML", output.Content);
         }
 
-        [Theory]
-        [InlineData("")]
-        [InlineData(null)]
-        public async Task ProcessAsync_DoesNothingIfNullOrEmptyValidationSummaryValue(string validationSummaryValue)
+        [Fact]
+        public async Task ProcessAsync_DoesNothingIfValidationSummaryNone()
         {
             // Arrange
             var validationSummaryTagHelper = new ValidationSummaryTagHelper
             {
-                ValidationSummaryValue = validationSummaryValue
+                ValidationSummary = ValidationSummary.None,
             };
             var output = new TagHelperOutput(
                 "div",
@@ -166,16 +185,14 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         }
 
         [Theory]
-        [InlineData("All")]
-        [InlineData("all")]
-        [InlineData("ModelOnly")]
-        [InlineData("modelonly")]
-        public async Task ProcessAsync_GeneratesValidationSummaryWhenNotNone_IgnoresCase(string validationSummary)
+        [InlineData(ValidationSummary.All)]
+        [InlineData(ValidationSummary.ModelOnly)]
+        public async Task ProcessAsync_GeneratesValidationSummaryWhenNotNone(ValidationSummary validationSummary)
         {
             // Arrange
             var validationSummaryTagHelper = new ValidationSummaryTagHelper
             {
-                ValidationSummaryValue = validationSummary
+                ValidationSummary = validationSummary,
             };
             var output = new TagHelperOutput(
                 "div",
@@ -211,56 +228,24 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         }
 
         [Theory]
-        [InlineData("None")]
-        [InlineData("none")]
-        public async Task ProcessAsync_DoesNotGenerateValidationSummaryWhenNone_IgnoresCase(string validationSummary)
+        [InlineData((ValidationSummary)(-1))]
+        [InlineData((ValidationSummary)23)]
+        [InlineData(ValidationSummary.All | ValidationSummary.ModelOnly)]
+        [ReplaceCulture]
+        public void ValidationSummaryProperty_ThrowsWhenSetToInvalidValidationSummaryValue(
+            ValidationSummary validationSummary)
         {
             // Arrange
-            var validationSummaryTagHelper = new ValidationSummaryTagHelper
-            {
-                ValidationSummaryValue = validationSummary
-            };
-            var output = new TagHelperOutput(
-                "div",
-                attributes: new Dictionary<string, string>(),
-                content: "Content of validation message");
-            var tagBuilder = new TagBuilder("span2")
-            {
-                InnerHtml = "New HTML"
-            };
+            var validationSummaryTagHelper = new ValidationSummaryTagHelper();
+            var expectedMessage = string.Format(
+                @"The value of argument 'value' ({0}) is invalid for Enum type 'Microsoft.AspNet.Mvc.ValidationSummary'.
+Parameter name: value",
+                validationSummary);
 
-            var generator = new Mock<IHtmlGenerator>(MockBehavior.Strict);
-
-            // Act
-            await validationSummaryTagHelper.ProcessAsync(context: null, output: output);
-
-            // Assert
-            Assert.Equal("div", output.TagName);
-            Assert.Empty(output.Attributes);
-            Assert.Equal("Content of validation message", output.Content);
-        }
-
-        [Fact]
-        public async Task ProcessAsync_ThrowsWhenInvalidValidationSummaryValue()
-        {
-            // Arrange
-            var validationSummaryTagHelper = new ValidationSummaryTagHelper
-            {
-                ValidationSummaryValue = "Hello World"
-            };
-            var output = new TagHelperOutput(
-                "div",
-                attributes: new Dictionary<string, string>(),
-                content: "Content of validation message");
-            var expectedViewContext = CreateViewContext();
-            var expectedMessage = "Cannot parse 'asp-validation-summary' value 'Hello World' for <div>. Acceptable " +
-                                  "values are 'All', 'ModelOnly' and 'None'.";
-
-            // Act
-            var ex = await Assert.ThrowsAsync<InvalidOperationException>(
-                () => validationSummaryTagHelper.ProcessAsync(context: null, output: output));
-
-            // Assert
+            // Act & Assert
+            var ex = Assert.Throws<ArgumentException>(
+                "value",
+                () => { validationSummaryTagHelper.ValidationSummary = validationSummary; });
             Assert.Equal(expectedMessage, ex.Message);
         }
 
diff --git a/test/WebSites/MvcTagHelpersWebSite/Views/MvcTagHelper_Home/CreateWarehouse.cshtml b/test/WebSites/MvcTagHelpersWebSite/Views/MvcTagHelper_Home/CreateWarehouse.cshtml
index 8e2063b18d..8502487954 100644
--- a/test/WebSites/MvcTagHelpersWebSite/Views/MvcTagHelper_Home/CreateWarehouse.cshtml
+++ b/test/WebSites/MvcTagHelpersWebSite/Views/MvcTagHelper_Home/CreateWarehouse.cshtml
@@ -20,7 +20,7 @@
             <select asp-for="Product" asp-items="(IEnumerable<SelectListItem>)ViewBag.Items" />
             <span asp-validation-for="Product" />
         </div>
-        <div asp-validation-summary="All" class="warehouse" />
+        <div asp-validation-summary="ValidationSummary.All" class="warehouse" />
         <input type="submit" />
     }
 </body>
diff --git a/test/WebSites/MvcTagHelpersWebSite/Views/MvcTagHelper_Home/Order.cshtml b/test/WebSites/MvcTagHelpersWebSite/Views/MvcTagHelper_Home/Order.cshtml
index 703213b130..a380d5d4e4 100644
--- a/test/WebSites/MvcTagHelpersWebSite/Views/MvcTagHelper_Home/Order.cshtml
+++ b/test/WebSites/MvcTagHelpersWebSite/Views/MvcTagHelper_Home/Order.cshtml
@@ -75,7 +75,7 @@
             @Html.EditorFor(model => model.Customer.Gender)
             <span asp-validation-for="Customer.Gender" />
         </div>
-        <div asp-validation-summary="All" class="order" />
+        <div asp-validation-summary="ValidationSummary.All" class="order" />
         <input type="hidden" asp-for="Customer.Key" />
         <input type="submit" />
     </form>
diff --git a/test/WebSites/MvcTagHelpersWebSite/Views/Shared/Customer.cshtml b/test/WebSites/MvcTagHelpersWebSite/Views/Shared/Customer.cshtml
index c26d5646ce..8209b65bda 100644
--- a/test/WebSites/MvcTagHelpersWebSite/Views/Shared/Customer.cshtml
+++ b/test/WebSites/MvcTagHelpersWebSite/Views/Shared/Customer.cshtml
@@ -38,8 +38,8 @@
             <input asp-for="Gender" type="radio" value="Female" /> Female
             <span asp-validation-for="Gender" />
         </div>
-        <div asp-validation-summary="All" class="order" />
-        <div asp-validation-summary="ModelOnly" class="order" />
+        <div asp-validation-summary="ValidationSummary.All" class="order" />
+        <div asp-validation-summary="ValidationSummary.ModelOnly" class="order" />
         <input type="submit" />
     </form>
 </body>
diff --git a/test/WebSites/TagHelpersWebSite/Views/Employee/Create.cshtml b/test/WebSites/TagHelpersWebSite/Views/Employee/Create.cshtml
index f1f7600819..f0c961cc89 100644
--- a/test/WebSites/TagHelpersWebSite/Views/Employee/Create.cshtml
+++ b/test/WebSites/TagHelpersWebSite/Views/Employee/Create.cshtml
@@ -22,7 +22,7 @@
         <div class="form-horizontal">
             <h4>Employee</h4>
             <hr />
-            <div asp-validation-summary="All" class="text-danger">
+            <div asp-validation-summary="ValidationSummary.All" class="text-danger">
             </div>
             <div class="form-group">
                 <label asp-for="Age" class="control-label col-md-2" />