Add a <partial /> tag helper

Fixes #5916

src/Microsoft.AspNetCore.Mvc.Razor/IRazorViewEngine.cs

@@ -15,9 +15,13 @@ namespace Microsoft.AspNetCore.Mvc.Razor
         /// <paramref name="context"/>.
         /// </summary>
         /// <param name="context">The <see cref="ActionContext"/>.</param>
-        /// <param name="pageName">The name of the page.</param>
+        /// <param name="pageName">The name or path of the page.</param>
         /// <returns>The <see cref="RazorPageResult"/> of locating the page.</returns>
-        /// <remarks><seealso cref="IViewEngine.FindView"/>.</remarks>
+        /// <remarks>
+        /// <remarks>Use <see cref="GetPage(string, string)"/> when the absolute or relative
+        /// path of the page is known.</remarks>
+        /// <seealso cref="IViewEngine.FindView"/>.
+        /// </remarks>
         RazorPageResult FindPage(ActionContext context, string pageName);
 
         /// <summary>

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

@@ -0,0 +1,119 @@
+// 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 System;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc.Rendering;
+using Microsoft.AspNetCore.Mvc.ViewEngines;
+using Microsoft.AspNetCore.Mvc.ViewFeatures;
+using Microsoft.AspNetCore.Mvc.ViewFeatures.Internal;
+using Microsoft.AspNetCore.Razor.TagHelpers;
+
+namespace Microsoft.AspNetCore.Mvc.TagHelpers
+{
+    /// <summary>
+    /// Renders a partial view.
+    /// </summary>
+    [HtmlTargetElement("partial", Attributes = "name", TagStructure = TagStructure.WithoutEndTag)]
+    public class PartialTagHelper : TagHelper
+    {
+        private const string ForAttributeName = "asp-for";
+        private readonly ICompositeViewEngine _viewEngine;
+        private readonly IViewBufferScope _viewBufferScope;
+
+        public PartialTagHelper(
+            ICompositeViewEngine viewEngine,
+            IViewBufferScope viewBufferScope)
+        {
+            _viewEngine = viewEngine ?? throw new ArgumentNullException(nameof(viewEngine));
+            _viewBufferScope = viewBufferScope ?? throw new ArgumentNullException(nameof(viewBufferScope));
+        }
+
+        /// <summary>
+        /// The name or path of the partial view that is rendered to the response.
+        /// </summary>
+        public string Name { get; set; }
+
+        /// <summary>
+        /// An expression to be evaluated against the current model.
+        /// </summary>
+        [HtmlAttributeName(ForAttributeName)]
+        public ModelExpression For { get; set; }
+
+        /// <summary>
+        /// A <see cref="ViewDataDictionary"/> to pass into the partial view.
+        /// </summary>
+        public ViewDataDictionary ViewData { get; set; }
+
+        [HtmlAttributeNotBound]
+        [ViewContext]
+        public ViewContext ViewContext { get; set; }
+
+        /// <inheritdoc />
+        public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (output == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            var viewBuffer = new ViewBuffer(_viewBufferScope, Name, ViewBuffer.PartialViewPageSize);
+            using (var writer = new ViewBufferTextWriter(viewBuffer, Encoding.UTF8))
+            {
+                await RenderPartialViewAsync(writer);
+
+                // Reset the TagName. We don't want `partial` to render.
+                output.TagName = null;
+                output.Content.SetHtmlContent(viewBuffer);
+            }
+        }
+
+        private async Task RenderPartialViewAsync(TextWriter writer)
+        {
+            var viewEngineResult = _viewEngine.GetView(ViewContext.ExecutingFilePath, Name, isMainPage: false);
+            var getViewLocations = viewEngineResult.SearchedLocations;
+            if (!viewEngineResult.Success)
+            {
+                viewEngineResult = _viewEngine.FindView(ViewContext, Name, isMainPage: false);
+            }
+
+            if (!viewEngineResult.Success)
+            {
+                var searchedLocations = Enumerable.Concat(getViewLocations, viewEngineResult.SearchedLocations);
+                var locations = string.Empty;
+                if (searchedLocations.Any())
+                {
+                    locations += Environment.NewLine + string.Join(Environment.NewLine, searchedLocations);
+                }
+
+                throw new InvalidOperationException(
+                    Resources.FormatViewEngine_PartialViewNotFound(Name, locations));
+            }
+
+            var view = viewEngineResult.View;
+            // Determine which ViewData we should use to construct a new ViewData
+            var baseViewData = ViewData ?? ViewContext.ViewData;
+            var model = For?.Model ?? ViewContext.ViewData.Model;
+            var newViewData = new ViewDataDictionary<object>(baseViewData, model);
+            var partialViewContext = new ViewContext(ViewContext, view, newViewData, writer);
+
+            if (For?.Name != null)
+            {
+                newViewData.TemplateInfo.HtmlFieldPrefix = newViewData.TemplateInfo.GetFullHtmlFieldName(For.Name);
+            }
+
+            using (view as IDisposable)
+            {
+                await view.RenderAsync(partialViewContext);
+            }
+        }
+    }
+}

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

@@ -178,6 +178,20 @@ namespace Microsoft.AspNetCore.Mvc.TagHelpers
         internal static string FormatArgumentCannotContainHtmlSpace()
             => GetString("ArgumentCannotContainHtmlSpace");
 
+        /// <summary>
+        /// The partial view '{0}' was not found. The following locations were searched:{1}
+        /// </summary>
+        internal static string ViewEngine_PartialViewNotFound
+        {
+            get => GetString("ViewEngine_PartialViewNotFound");
+        }
+
+        /// <summary>
+        /// The partial view '{0}' was not found. The following locations were searched:{1}
+        /// </summary>
+        internal static string FormatViewEngine_PartialViewNotFound(object p0, object p1)
+            => string.Format(CultureInfo.CurrentCulture, GetString("ViewEngine_PartialViewNotFound"), p0, p1);
+
         private static string GetString(string name, params string[] formatterNames)
         {
             var value = _resourceManager.GetString(name);

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

@@ -153,4 +153,7 @@
   <data name="ArgumentCannotContainHtmlSpace" xml:space="preserve">
     <value>Value cannot contain HTML space characters.</value>
   </data>
+  <data name="ViewEngine_PartialViewNotFound" xml:space="preserve">
+    <value>The partial view '{0}' was not found. The following locations were searched:{1}</value>
+  </data>
 </root>

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

@@ -108,7 +108,7 @@ namespace Microsoft.AspNetCore.Mvc
         /// <summary>
         /// Creates a <see cref="ViewResult"/> object by specifying a <paramref name="viewName"/>.
         /// </summary>
-        /// <param name="viewName">The name of the view that is rendered to the response.</param>
+        /// <param name="viewName">The name or path of the view that is rendered to the response.</param>
         /// <returns>The created <see cref="ViewResult"/> object for the response.</returns>
         [NonAction]
         public virtual ViewResult View(string viewName)
@@ -132,7 +132,7 @@ namespace Microsoft.AspNetCore.Mvc
         /// Creates a <see cref="ViewResult"/> object by specifying a <paramref name="viewName"/>
         /// and the <paramref name="model"/> to be rendered by the view.
         /// </summary>
-        /// <param name="viewName">The name of the view that is rendered to the response.</param>
+        /// <param name="viewName">The name or path of the view that is rendered to the response.</param>
         /// <param name="model">The model that is rendered by the view.</param>
         /// <returns>The created <see cref="ViewResult"/> object for the response.</returns>
         [NonAction]
@@ -161,7 +161,7 @@ namespace Microsoft.AspNetCore.Mvc
         /// <summary>
         /// Creates a <see cref="PartialViewResult"/> object by specifying a <paramref name="viewName"/>.
         /// </summary>
-        /// <param name="viewName">The name of the view that is rendered to the response.</param>
+        /// <param name="viewName">The name or path of the partial view that is rendered to the response.</param>
         /// <returns>The created <see cref="PartialViewResult"/> object for the response.</returns>
         [NonAction]
         public virtual PartialViewResult PartialView(string viewName)
@@ -185,7 +185,7 @@ namespace Microsoft.AspNetCore.Mvc
         /// Creates a <see cref="PartialViewResult"/> object by specifying a <paramref name="viewName"/>
         /// and the <paramref name="model"/> to be rendered by the partial view.
         /// </summary>
-        /// <param name="viewName">The name of the partial view that is rendered to the response.</param>
+        /// <param name="viewName">The name or path of the partial view that is rendered to the response.</param>
         /// <param name="model">The model that is rendered by the partial view.</param>
         /// <returns>The created <see cref="PartialViewResult"/> object for the response.</returns>
         [NonAction]

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

@@ -7,7 +7,6 @@ using Microsoft.AspNetCore.Mvc.Controllers;
 using Microsoft.AspNetCore.Mvc.Infrastructure;
 using Microsoft.AspNetCore.Mvc.ViewEngines;
 using Microsoft.AspNetCore.Mvc.ViewFeatures;
-using Microsoft.AspNetCore.Mvc.ViewFeatures.Internal;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace Microsoft.AspNetCore.Mvc
@@ -23,7 +22,7 @@ namespace Microsoft.AspNetCore.Mvc
         public int? StatusCode { get; set; }
 
         /// <summary>
-        /// Gets or sets the name of the partial view to render.
+        /// Gets or sets the name or path of the partial view that is rendered to the response.
         /// </summary>
         /// <remarks>
         /// When <c>null</c>, defaults to <see cref="ControllerActionDescriptor.ActionName"/>.

src/Microsoft.AspNetCore.Mvc.ViewFeatures/Rendering/HtmlHelperPartialExtensions.cs

@@ -18,7 +18,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <returns>
         /// A <see cref="Task"/> that on completion returns a new <see cref="IHtmlContent"/> instance containing
@@ -46,7 +46,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <param name="viewData">A <see cref="ViewDataDictionary"/> to pass into the partial view.</param>
         /// <returns>
@@ -76,7 +76,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <param name="model">A model to pass into the partial view.</param>
         /// <returns>
@@ -106,7 +106,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <returns>
         /// Returns a new <see cref="IHtmlContent"/> instance containing the created HTML.
@@ -137,7 +137,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <param name="viewData">A <see cref="ViewDataDictionary"/> to pass into the partial view.</param>
         /// <returns>
@@ -170,7 +170,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <param name="model">A model to pass into the partial view.</param>
         /// <returns>
@@ -203,7 +203,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <param name="model">A model to pass into the partial view.</param>
         /// <param name="viewData">A <see cref="ViewDataDictionary"/> to pass into the partial view.</param>
@@ -239,7 +239,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <remarks>
         /// In this context, "renders" means the method writes its output using <see cref="ViewContext.Writer"/>.
@@ -267,7 +267,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <param name="viewData">A <see cref="ViewDataDictionary"/> to pass into the partial view.</param>
         /// <remarks>
@@ -297,7 +297,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <param name="model">A model to pass into the partial view.</param>
         /// <remarks>
@@ -327,7 +327,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <returns>A <see cref="Task"/> that renders the created HTML when it executes.</returns>
         /// <remarks>
@@ -355,7 +355,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <param name="viewData">A <see cref="ViewDataDictionary"/> to pass into the partial view.</param>
         /// <returns>A <see cref="Task"/> that renders the created HTML when it executes.</returns>
@@ -385,7 +385,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// </summary>
         /// <param name="htmlHelper">The <see cref="IHtmlHelper"/> instance this method extends.</param>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <param name="model">A model to pass into the partial view.</param>
         /// <returns>A <see cref="Task"/> that renders the created HTML when it executes.</returns>

src/Microsoft.AspNetCore.Mvc.ViewFeatures/Rendering/IHtmlHelper.cs

@@ -570,7 +570,7 @@ namespace Microsoft.AspNetCore.Mvc.Rendering
         /// Renders HTML markup for the specified partial view.
         /// </summary>
         /// <param name="partialViewName">
-        /// The name of the partial view used to create the HTML markup. Must not be <c>null</c>.
+        /// The name or path of the partial view used to create the HTML markup. Must not be <c>null</c>.
         /// </param>
         /// <param name="model">A model to pass into the partial view.</param>
         /// <param name="viewData">A <see cref="ViewDataDictionary"/> to pass into the partial view.</param>

src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewEngines/IViewEngine.cs

@@ -13,9 +13,11 @@ namespace Microsoft.AspNetCore.Mvc.ViewEngines
         /// <paramref name="context"/>.
         /// </summary>
         /// <param name="context">The <see cref="ActionContext"/>.</param>
-        /// <param name="viewName">The name of the view.</param>
+        /// <param name="viewName">The name or path of the view that is rendered to the response.</param>
         /// <param name="isMainPage">Determines if the page being found is the main page for an action.</param>
         /// <returns>The <see cref="ViewEngineResult"/> of locating the view.</returns>
+        /// <remarks>Use <see cref="GetView(string, string, bool)"/> when the absolute or relative
+        /// path of the view is known.</remarks>
         ViewEngineResult FindView(ActionContext context, string viewName, bool isMainPage);
 
         /// <summary>

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

@@ -7,7 +7,6 @@ using Microsoft.AspNetCore.Mvc.Controllers;
 using Microsoft.AspNetCore.Mvc.Infrastructure;
 using Microsoft.AspNetCore.Mvc.ViewEngines;
 using Microsoft.AspNetCore.Mvc.ViewFeatures;
-using Microsoft.AspNetCore.Mvc.ViewFeatures.Internal;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace Microsoft.AspNetCore.Mvc
@@ -23,7 +22,7 @@ namespace Microsoft.AspNetCore.Mvc
         public int? StatusCode { get; set; }
 
         /// <summary>
-        /// Gets or sets the name of the view to render.
+        /// Gets or sets the name or path of the view that is rendered to the response.
         /// </summary>
         /// <remarks>
         /// When <c>null</c>, defaults to <see cref="ControllerActionDescriptor.ActionName"/>.

test/Microsoft.AspNetCore.Mvc.FunctionalTests/HtmlGenerationTest.cs

@@ -61,8 +61,12 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
                     // Only attribute order should differ.
                     { "Order", "/HtmlGeneration_Order/Submit" },
                     { "OrderUsingHtmlHelpers", "/HtmlGeneration_Order/Submit" },
+                    // Testing PartialTagHelper
+                    { "PartialTagHelperWithoutModel", null },
+                    { "Warehouse", null },
                     // Testing InputTagHelpers invoked in the partial views
                     { "ProductList", "/HtmlGeneration_Product" },
+                    { "ProductListUsingTagHelpers", "/HtmlGeneration_Product" },
                     // Testing the ScriptTagHelper
                     { "Script", null },
                 };

test/Microsoft.AspNetCore.Mvc.FunctionalTests/compiler/resources/HtmlGenerationWebSite.HtmlGeneration_Home.PartialTagHelperWithoutModel.html

@@ -0,0 +1 @@
+PartialTagHelperWithoutModel: Hello from partial

test/Microsoft.AspNetCore.Mvc.FunctionalTests/compiler/resources/HtmlGenerationWebSite.HtmlGeneration_Home.ProductListUsingTagHelpers.html

@@ -0,0 +1,66 @@
+<html>
+<head>
+    <meta charset="utf-8" />
+</head>
+<body>
+    <form action="/HtmlGeneration_Product" method="post">
+            <div>
+                <label class="product" for="z0__HomePage">HomePage</label>
+                <input type="url" size="50" disabled="disabled" readonly="readonly" id="z0__HomePage" name="[0].HomePage" value="http://www.contoso.com/" />
+            </div>
+            
+<div>
+    <label class="product" for="z0__Number">Number</label>
+    <input type="number" data-val="true" data-val-required="The Number field is required." id="z0__Number" name="[0].Number" value="0" />
+</div>
+<div>
+    <label class="product" for="z0__ProductName">ProductName</label>
+    <input type="text" data-val="true" data-val-required="The ProductName field is required." id="z0__ProductName" name="[0].ProductName" value="Product_0" />
+</div>
+<div>
+    <label class="product" for="z0__Description">Description</label>
+    <textarea rows="4" cols="50" class="product" id="z0__Description" name="[0].Description">
+</textarea>
+</div>
+            <div>
+                <label class="product" for="z1__HomePage">HomePage</label>
+                <input type="url" size="50" disabled="disabled" readonly="readonly" id="z1__HomePage" name="[1].HomePage" value="" />
+            </div>
+            
+<div>
+    <label class="product" for="z1__Number">Number</label>
+    <input type="number" data-val="true" data-val-required="The Number field is required." id="z1__Number" name="[1].Number" value="1" />
+</div>
+<div>
+    <label class="product" for="z1__ProductName">ProductName</label>
+    <input type="text" data-val="true" data-val-required="The ProductName field is required." id="z1__ProductName" name="[1].ProductName" value="Product_1" />
+</div>
+<div>
+    <label class="product" for="z1__Description">Description</label>
+    <textarea rows="4" cols="50" class="product" id="z1__Description" name="[1].Description">
+</textarea>
+</div>
+            <div>
+                <label class="product" for="z2__HomePage">HomePage</label>
+                <input type="url" size="50" disabled="disabled" readonly="readonly" id="z2__HomePage" name="[2].HomePage" value="" />
+            </div>
+            
+<div>
+    <label class="product" for="z2__Number">Number</label>
+    <input type="number" data-val="true" data-val-required="The Number field is required." id="z2__Number" name="[2].Number" value="2" />
+</div>
+<div>
+    <label class="product" for="z2__ProductName">ProductName</label>
+    <input type="text" data-val="true" data-val-required="The ProductName field is required." id="z2__ProductName" name="[2].ProductName" value="Product_2" />
+</div>
+<div>
+    <label class="product" for="z2__Description">Description</label>
+    <textarea rows="4" cols="50" class="product" id="z2__Description" name="[2].Description">
+Product_2 description</textarea>
+</div>
+        
+        <div>HtmlFieldPrefix = </div>
+        <input type="submit" />
+    <input name="__RequestVerificationToken" type="hidden" value="{0}" /></form>
+</body>
+</html>

test/Microsoft.AspNetCore.Mvc.FunctionalTests/compiler/resources/HtmlGenerationWebSite.HtmlGeneration_Home.Warehouse.html

@@ -0,0 +1,15 @@
+<h3>City_1</h3>
+
+<div>
+    <label for="Employee_Name">Name</label>
+    <input type="text" id="Employee_Name" name="Employee.Name" value="EmployeeName_1" />
+</div>
+<div>
+    <label for="Employee_OfficeNumber">OfficeNumber</label>
+    <input type="number" id="Employee_OfficeNumber" name="Employee.OfficeNumber" value="Number_1" />
+</div>
+<div>
+    <label for="Employee_Address">Address</label>
+    <textarea rows="4" cols="50" id="Employee_Address" name="Employee.Address">
+Address_1</textarea>
+</div>

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

@@ -0,0 +1,473 @@
+// 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 System;
+using System.Collections.Generic;
+using System.IO;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc.Abstractions;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+using Microsoft.AspNetCore.Mvc.Rendering;
+using Microsoft.AspNetCore.Mvc.TestCommon;
+using Microsoft.AspNetCore.Mvc.ViewEngines;
+using Microsoft.AspNetCore.Mvc.ViewFeatures;
+using Microsoft.AspNetCore.Mvc.ViewFeatures.Internal;
+using Microsoft.AspNetCore.Razor.TagHelpers;
+using Microsoft.AspNetCore.Routing;
+using Microsoft.Extensions.WebEncoders.Testing;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.TagHelpers
+{
+    public class PartialTagHelperTest
+    {
+        [Fact]
+        public async Task ProcessAsync_RendersPartialView_IfGetViewReturnsView()
+        {
+            // Arrange
+            var expected = "Hello world!";
+            var bufferScope = new TestViewBufferScope();
+            var partialName = "_Partial";
+            var model = new object();
+            var viewContext = GetViewContext();
+
+            var view = new Mock<IView>();
+            view.Setup(v => v.RenderAsync(It.IsAny<ViewContext>()))
+                .Callback((ViewContext v) =>
+                {
+                    v.Writer.Write(expected);
+                })
+                .Returns(Task.CompletedTask);
+
+            var viewEngine = new Mock<ICompositeViewEngine>();
+            viewEngine.Setup(v => v.GetView(It.IsAny<string>(), partialName, false))
+                .Returns(ViewEngineResult.Found(partialName, view.Object));
+
+            var tagHelper = new PartialTagHelper(viewEngine.Object, bufferScope)
+            {
+                Name = partialName,
+                ViewContext = viewContext,
+            };
+            var tagHelperContext = GetTagHelperContext();
+            var output = GetTagHelperOutput();
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            var content = HtmlContentUtilities.HtmlContentToString(output.Content, new HtmlTestEncoder());
+            Assert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task ProcessAsync_RendersPartialView_IfFindViewReturnsView()
+        {
+            // Arrange
+            var expected = "Hello world!";
+            var bufferScope = new TestViewBufferScope();
+            var partialName = "_Partial";
+            var model = new object();
+            var viewContext = GetViewContext();
+
+            var view = new Mock<IView>();
+            view.Setup(v => v.RenderAsync(It.IsAny<ViewContext>()))
+                .Callback((ViewContext v) =>
+                {
+                    v.Writer.Write(expected);
+                })
+                .Returns(Task.CompletedTask);
+
+            var viewEngine = new Mock<ICompositeViewEngine>();
+            viewEngine.Setup(v => v.GetView(It.IsAny<string>(), partialName, false))
+                .Returns(ViewEngineResult.NotFound(partialName, new[] { partialName }));
+
+            viewEngine.Setup(v => v.FindView(viewContext, partialName, false))
+                .Returns(ViewEngineResult.Found(partialName, view.Object));
+
+            var tagHelper = new PartialTagHelper(viewEngine.Object, bufferScope)
+            {
+                Name = partialName,
+                ViewContext = viewContext,
+            };
+            var tagHelperContext = GetTagHelperContext();
+            var output = GetTagHelperOutput();
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            var content = HtmlContentUtilities.HtmlContentToString(output.Content, new HtmlTestEncoder());
+            Assert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task ProcessAsync_UsesViewDataFromContext()
+        {
+            // Arrange
+            var expected = "Implicit";
+            var bufferScope = new TestViewBufferScope();
+            var partialName = "_Partial";
+            var viewContext = GetViewContext();
+            viewContext.ViewData["key"] = expected;
+
+            var view = new Mock<IView>();
+            view.Setup(v => v.RenderAsync(It.IsAny<ViewContext>()))
+                .Callback((ViewContext v) =>
+                {
+                    v.Writer.Write(v.ViewData["key"]);
+                })
+                .Returns(Task.CompletedTask);
+
+            var viewEngine = new Mock<ICompositeViewEngine>();
+            viewEngine.Setup(v => v.GetView(It.IsAny<string>(), partialName, false))
+                .Returns(ViewEngineResult.NotFound(partialName, new[] { partialName }));
+
+            viewEngine.Setup(v => v.FindView(viewContext, partialName, false))
+                .Returns(ViewEngineResult.Found(partialName, view.Object));
+
+            var tagHelper = new PartialTagHelper(viewEngine.Object, bufferScope)
+            {
+                Name = partialName,
+                ViewContext = viewContext,
+            };
+            var tagHelperContext = GetTagHelperContext();
+            var output = GetTagHelperOutput();
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            var content = HtmlContentUtilities.HtmlContentToString(output.Content, new HtmlTestEncoder());
+            Assert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task ProcessAsync_UsesPassedInViewData_WhenNotNull()
+        {
+            // Arrange
+            var expected = "Explicit";
+            var bufferScope = new TestViewBufferScope();
+            var partialName = "_Partial";
+            var model = new object();
+            var viewData = new ViewDataDictionary(new TestModelMetadataProvider(), new ModelStateDictionary());
+            viewData["key"] = expected;
+            var viewContext = GetViewContext();
+            viewContext.ViewData["key"] = "ViewContext";
+
+            var view = new Mock<IView>();
+            view.Setup(v => v.RenderAsync(It.IsAny<ViewContext>()))
+                .Callback((ViewContext v) =>
+                {
+                    v.Writer.Write(v.ViewData["key"]);
+                })
+                .Returns(Task.CompletedTask);
+
+            var viewEngine = new Mock<ICompositeViewEngine>();
+            viewEngine.Setup(v => v.GetView(It.IsAny<string>(), partialName, false))
+                .Returns(ViewEngineResult.Found(partialName, view.Object));
+
+            var tagHelper = new PartialTagHelper(viewEngine.Object, bufferScope)
+            {
+                Name = partialName,
+                ViewContext = viewContext,
+                ViewData = viewData,
+            };
+            var tagHelperContext = GetTagHelperContext();
+            var output = GetTagHelperOutput();
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            var content = HtmlContentUtilities.HtmlContentToString(output.Content, new HtmlTestEncoder());
+            Assert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task ProcessAsync_UsesModelExpression_ToDetermineModel()
+        {
+            // Arrange
+            var expected = new PropertyModel();
+            var bufferScope = new TestViewBufferScope();
+            var partialName = "_Partial";
+            var modelMetadataProvider = new TestModelMetadataProvider();
+            var containerModel = new TestModel { Property = expected };
+            var containerModelExplorer = modelMetadataProvider.GetModelExplorerForType(
+                typeof(TestModel),
+                containerModel);
+            var propertyModelExplorer = containerModelExplorer.GetExplorerForProperty(nameof(TestModel.Property));
+
+            var modelExpression = new ModelExpression("Property", propertyModelExplorer);
+            var viewContext = GetViewContext();
+            viewContext.ViewData.Model = new object();
+
+            var view = new Mock<IView>();
+            view.Setup(v => v.RenderAsync(It.IsAny<ViewContext>()))
+                .Callback((ViewContext v) =>
+                {
+                    var actual = Assert.IsType<PropertyModel>(v.ViewData.Model);
+                    Assert.Same(expected, actual);
+                })
+                .Returns(Task.CompletedTask)
+                .Verifiable();
+
+            var viewEngine = new Mock<ICompositeViewEngine>();
+            viewEngine.Setup(v => v.GetView(It.IsAny<string>(), partialName, false))
+                .Returns(ViewEngineResult.Found(partialName, view.Object));
+
+            var tagHelper = new PartialTagHelper(viewEngine.Object, bufferScope)
+            {
+                Name = partialName,
+                ViewContext = viewContext,
+                For = modelExpression,
+            };
+            var tagHelperContext = GetTagHelperContext();
+            var output = GetTagHelperOutput();
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            view.Verify();
+        }
+
+        [Fact]
+        public async Task ProcessAsync_SetsHtmlFieldPrefix_UsingModelExpression()
+        {
+            // Arrange
+            var expected = "order.items[0].Property";
+            var bufferScope = new TestViewBufferScope();
+            var partialName = "_Partial";
+            var modelMetadataProvider = new TestModelMetadataProvider();
+            var containerModel = new TestModel { Property = new PropertyModel() };
+            var containerModelExplorer = modelMetadataProvider.GetModelExplorerForType(
+                typeof(TestModel),
+                containerModel);
+            var propertyModelExplorer = containerModelExplorer.GetExplorerForProperty(nameof(TestModel.Property));
+
+            var modelExpression = new ModelExpression("Property", propertyModelExplorer);
+            var viewContext = GetViewContext();
+            viewContext.ViewData.TemplateInfo.HtmlFieldPrefix = "order.items[0]";
+
+            var view = new Mock<IView>();
+            view.Setup(v => v.RenderAsync(It.IsAny<ViewContext>()))
+                .Callback((ViewContext v) =>
+                {
+                    Assert.Equal(expected, v.ViewData.TemplateInfo.HtmlFieldPrefix);
+                })
+                .Returns(Task.CompletedTask)
+                .Verifiable();
+
+            var viewEngine = new Mock<ICompositeViewEngine>();
+            viewEngine.Setup(v => v.GetView(It.IsAny<string>(), partialName, false))
+                .Returns(ViewEngineResult.Found(partialName, view.Object));
+
+            var tagHelper = new PartialTagHelper(viewEngine.Object, bufferScope)
+            {
+                Name = partialName,
+                ViewContext = viewContext,
+                For = modelExpression,
+            };
+            var tagHelperContext = GetTagHelperContext();
+            var output = GetTagHelperOutput();
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            view.Verify();
+            Assert.Equal("order.items[0]", viewContext.ViewData.TemplateInfo.HtmlFieldPrefix);
+        }
+
+        [Fact]
+        public async Task ProcessAsync_UsesModelOnViewContextViewData_WhenModelExpresionIsNull()
+        {
+            // Arrange
+            var bufferScope = new TestViewBufferScope();
+            var partialName = "_Partial";
+            var model = new object();
+            var viewContext = GetViewContext();
+            viewContext.ViewData.Model = model;
+
+            var view = new Mock<IView>();
+            view.Setup(v => v.RenderAsync(It.IsAny<ViewContext>()))
+                .Callback((ViewContext v) =>
+                {
+                    Assert.Same(model, v.ViewData.Model);
+                })
+                .Returns(Task.CompletedTask)
+                .Verifiable();
+
+            var viewEngine = new Mock<ICompositeViewEngine>();
+            viewEngine.Setup(v => v.GetView(It.IsAny<string>(), partialName, false))
+                .Returns(ViewEngineResult.Found(partialName, view.Object));
+
+            var tagHelper = new PartialTagHelper(viewEngine.Object, bufferScope)
+            {
+                Name = partialName,
+                ViewContext = viewContext,
+            };
+            var tagHelperContext = GetTagHelperContext();
+            var output = GetTagHelperOutput();
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            view.Verify();
+        }
+
+        [Fact]
+        public async Task ProcessAsync_DoesNotModifyHtmlFieldPrefix_WhenModelExpressionIsNull()
+        {
+            // Arrange
+            var expected = "original";
+            var bufferScope = new TestViewBufferScope();
+            var partialName = "_Partial";
+            var model = new object();
+            var viewContext = GetViewContext();
+            viewContext.ViewData.Model = model;
+            viewContext.ViewData.TemplateInfo.HtmlFieldPrefix = expected;
+
+            var view = new Mock<IView>();
+            view.Setup(v => v.RenderAsync(It.IsAny<ViewContext>()))
+                .Callback((ViewContext v) =>
+                {
+                    Assert.Equal(expected, v.ViewData.TemplateInfo.HtmlFieldPrefix);
+                })
+                .Returns(Task.CompletedTask)
+                .Verifiable();
+
+            var viewEngine = new Mock<ICompositeViewEngine>();
+            viewEngine.Setup(v => v.GetView(It.IsAny<string>(), partialName, false))
+                .Returns(ViewEngineResult.Found(partialName, view.Object));
+
+            var tagHelper = new PartialTagHelper(viewEngine.Object, bufferScope)
+            {
+                Name = partialName,
+                ViewContext = viewContext,
+            };
+            var tagHelperContext = GetTagHelperContext();
+            var output = GetTagHelperOutput();
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            view.Verify();
+        }
+
+        [Fact]
+        public async Task ProcessAsync_DisposesViewInstance()
+        {
+            // Arrange
+            var bufferScope = new TestViewBufferScope();
+            var partialName = "_Partial";
+            var viewContext = GetViewContext();
+
+            var disposable = new Mock<IDisposable>();
+            disposable.Setup(d => d.Dispose()).Verifiable();
+            var view = disposable.As<IView>();
+
+            view.Setup(v => v.RenderAsync(It.IsAny<ViewContext>()))
+                .Returns(Task.CompletedTask)
+                .Verifiable();
+
+            var viewEngine = new Mock<ICompositeViewEngine>();
+            viewEngine.Setup(v => v.GetView(It.IsAny<string>(), partialName, false))
+                .Returns(ViewEngineResult.Found(partialName, view.Object));
+
+            var tagHelper = new PartialTagHelper(viewEngine.Object, bufferScope)
+            {
+                Name = partialName,
+                ViewContext = viewContext,
+            };
+            var tagHelperContext = GetTagHelperContext();
+            var output = GetTagHelperOutput();
+
+            // Act
+            await tagHelper.ProcessAsync(tagHelperContext, output);
+
+            // Assert
+            disposable.Verify();
+            view.Verify();
+        }
+
+        [Fact]
+        public async Task ProcessAsync_Throws_IfGetViewAndFindReturnNotFoundResults()
+        {
+            // Arrange
+            var bufferScope = new TestViewBufferScope();
+            var partialName = "_Partial";
+            var expected = string.Join(Environment.NewLine,
+                $"The partial view '{partialName}' was not found. The following locations were searched:",
+                "NotFound1",
+                "NotFound2",
+                "NotFound3",
+                "NotFound4");
+            var viewData = new ViewDataDictionary(new TestModelMetadataProvider(), new ModelStateDictionary());
+            var viewContext = GetViewContext();
+
+            var view = Mock.Of<IView>();
+            var viewEngine = new Mock<ICompositeViewEngine>();
+            viewEngine.Setup(v => v.GetView(It.IsAny<string>(), partialName, false))
+                .Returns(ViewEngineResult.NotFound(partialName, new[] { "NotFound1", "NotFound2" }));
+
+            viewEngine.Setup(v => v.FindView(viewContext, partialName, false))
+                .Returns(ViewEngineResult.NotFound(partialName, new[] { $"NotFound3", $"NotFound4" }));
+
+            var tagHelper = new PartialTagHelper(viewEngine.Object, bufferScope)
+            {
+                Name = partialName,
+                ViewContext = viewContext,
+                ViewData = viewData,
+            };
+            var tagHelperContext = GetTagHelperContext();
+            var output = GetTagHelperOutput();
+
+            // Act & Assert
+            var exception = await Assert.ThrowsAsync<InvalidOperationException>(
+                () => tagHelper.ProcessAsync(tagHelperContext, output));
+            Assert.Equal(expected, exception.Message);
+        }
+
+        private static ViewContext GetViewContext()
+        {
+            return new ViewContext(
+                new ActionContext(new DefaultHttpContext(), new RouteData(), new ActionDescriptor()),
+                NullView.Instance,
+                new ViewDataDictionary(new TestModelMetadataProvider(), new ModelStateDictionary()),
+                Mock.Of<ITempDataDictionary>(),
+                TextWriter.Null,
+                new HtmlHelperOptions());
+        }
+
+        private static TagHelperContext GetTagHelperContext()
+        {
+            return new TagHelperContext(
+                "partial",
+                new TagHelperAttributeList(),
+                new Dictionary<object, object>(),
+                Guid.NewGuid().ToString("N"));
+        }
+
+        private static TagHelperOutput GetTagHelperOutput()
+        {
+            return new TagHelperOutput(
+                "partial",
+                new TagHelperAttributeList(),
+                (_, __) => Task.FromResult<TagHelperContent>(new DefaultTagHelperContent()));
+        }
+
+        private class TestModel
+        {
+            public PropertyModel Property { get; set; }
+        }
+
+        private class PropertyModel
+        {
+        }
+    }
+}

test/WebSites/HtmlGenerationWebSite/Controllers/HtmlGeneration_HomeController.cs

@@ -108,6 +108,8 @@ namespace HtmlGenerationWebSite.Controllers
             return View(_products);
         }
 
+        public IActionResult ProductListUsingTagHelpers() => View(_products);
+
         public IActionResult EmployeeList()
         {
             var employees = new List<Employee>
@@ -165,6 +167,22 @@ namespace HtmlGenerationWebSite.Controllers
             return View(warehouse);
         }
 
+        public IActionResult Warehouse()
+        {
+            var warehouse = new Warehouse
+            {
+                City = "City_1",
+                Employee = new Employee
+                {
+                    Name = "EmployeeName_1",
+                    OfficeNumber = "Number_1",
+                    Address = "Address_1",
+                }
+            };
+
+            return View(warehouse);
+        }
+
         public IActionResult Environment()
         {
             return View();
@@ -209,5 +227,7 @@ namespace HtmlGenerationWebSite.Controllers
         {
             return View();
         }
+
+        public IActionResult PartialTagHelperWithoutModel() => View();
     }
 }

test/WebSites/HtmlGenerationWebSite/Views/HtmlGeneration_Home/PartialTagHelperWithoutModel.cshtml

@@ -0,0 +1,2 @@
+@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
+PartialTagHelperWithoutModel: <partial name="../Shared/_Partial" />

test/WebSites/HtmlGenerationWebSite/Views/HtmlGeneration_Home/ProductListUsingTagHelpers.cshtml

@@ -0,0 +1,25 @@
+@using HtmlGenerationWebSite.Models
+@model IList<Product>
+
+@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
+
+<html>
+<head>
+    <meta charset="utf-8" />
+</head>
+<body>
+    <form asp-action="Index" asp-controller="HtmlGeneration_Product" asp-antiforgery="true">
+        @for (var i = 0; i < Model.Count; i++)
+        {
+            <div>
+                <label asp-for="@Model[i].HomePage" class="product"></label>
+                <input asp-for="@Model[i].HomePage" type="url" size="50" disabled="disabled" readonly="readonly" />
+            </div>
+            <partial name="_ProductPartial" asp-for="@Model[i]" />
+        }
+        @* Print the HtmlFieldPrefix outside of the partial tag helper to ensure it hasn't been modified *@
+        <div>HtmlFieldPrefix = @ViewData.TemplateInfo.HtmlFieldPrefix</div>
+        <input type="submit" />
+    </form>
+</body>
+</html>

test/WebSites/HtmlGenerationWebSite/Views/HtmlGeneration_Home/Warehouse.cshtml

@@ -0,0 +1,5 @@
+@model HtmlGenerationWebSite.Models.Warehouse
+@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
+
+<h3>@Html.DisplayFor(m => m.City)</h3>
+<partial name="_EmployeePartial" asp-for="Employee" />

test/WebSites/HtmlGenerationWebSite/Views/HtmlGeneration_Home/_EmployeePartial.cshtml

@@ -0,0 +1,15 @@
+@model HtmlGenerationWebSite.Models.Employee
+@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
+
+<div>
+    <label asp-for="Name"></label>
+    <input asp-for="Name" type="text"/>
+</div>
+<div>
+    <label asp-for="OfficeNumber"></label>
+    <input asp-for="OfficeNumber" type="number"/>
+</div>
+<div>
+    <label asp-for="Address"></label>
+    <textarea asp-for="Address" rows="4" cols="50"></textarea>
+</div>

test/WebSites/HtmlGenerationWebSite/Views/Shared/_Partial.cshtml

@@ -0,0 +1 @@
+Hello from partial