Add partial helper to Razor Page \ PageModel

Fixes #7885

src/Microsoft.AspNetCore.Mvc.RazorPages/PageBase.cs

@@ -1214,6 +1214,33 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages
         public virtual UnauthorizedResult Unauthorized()
             => new UnauthorizedResult();
 
+        /// <summary>
+        /// Creates a <see cref="PartialViewResult"/> by specifying the name of a partial to render.
+        /// </summary>
+        /// <param name="viewName">The partial name.</param>
+        /// <returns>The created <see cref="PartialViewResult"/> object for the response.</returns>
+        public virtual PartialViewResult Partial(string viewName)
+        {
+            return Partial(viewName, model: null);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="PartialViewResult"/> by specifying the name of a partial to render and the model object.
+        /// </summary>
+        /// <param name="viewName">The partial name.</param>
+        /// <param name="model">The model to be passed into the partial.</param>
+        /// <returns>The created <see cref="PartialViewResult"/> object for the response.</returns>
+        public virtual PartialViewResult Partial(string viewName, object model)
+        {
+            ViewContext.ViewData.Model = model;
+
+            return new PartialViewResult
+            {
+                ViewName = viewName,
+                ViewData = ViewContext.ViewData
+            };
+        }
+
         #region ViewComponentResult
         /// <summary>
         /// Creates a <see cref="ViewComponentResult"/> by specifying the name of a view component to render.

src/Microsoft.AspNetCore.Mvc.RazorPages/PageModel.cs

@@ -1614,6 +1614,33 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages
         public virtual UnauthorizedResult Unauthorized()
             => new UnauthorizedResult();
 
+        /// <summary>
+        /// Creates a <see cref="PartialViewResult"/> by specifying the name of a partial to render.
+        /// </summary>
+        /// <param name="viewName">The partial name.</param>
+        /// <returns>The created <see cref="PartialViewResult"/> object for the response.</returns>
+        public virtual PartialViewResult Partial(string viewName)
+        {
+            return Partial(viewName, model: null);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="PartialViewResult"/> by specifying the name of a partial to render and the model object.
+        /// </summary>
+        /// <param name="viewName">The partial name.</param>
+        /// <param name="model">The model to be passed into the partial.</param>
+        /// <returns>The created <see cref="PartialViewResult"/> object for the response.</returns>
+        public virtual PartialViewResult Partial(string viewName, object model)
+        {
+            ViewData.Model = model;
+
+            return new PartialViewResult
+            {
+                ViewName = viewName,
+                ViewData = ViewData
+            };
+        }
+
         #region ViewComponentResult
         /// <summary>
         /// Creates a <see cref="ViewComponentResult"/> by specifying the name of a view component to render.

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

@@ -1,10 +1,8 @@
 // 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.Linq;
 using System.Net.Http;
-using AngleSharp.Dom.Html;
 using AngleSharp.Parser.Html;
 
 namespace Microsoft.AspNetCore.Mvc.FunctionalTests
@@ -19,27 +17,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
             var parser = new HtmlParser();
             var htmlDocument = parser.Parse(htmlContent);
 
-            return RetrieveAntiforgeryToken(htmlDocument);
-        }
-
-        public static string RetrieveAntiforgeryToken(IHtmlDocument htmlDocument)
-        {
-            var hiddenInputs = htmlDocument.QuerySelectorAll("form input[type=hidden]");
-            foreach (var input in hiddenInputs)
-            {
-                if (!input.HasAttribute("name"))
-                {
-                    continue;
-                }
-
-                var name = input.GetAttribute("name");
-                if (name == "__RequestVerificationToken" || name == "HtmlEncode[[__RequestVerificationToken]]")
-                {
-                    return input.GetAttribute("value");
-                }
-            }
-
-            throw new Exception($"Antiforgery token could not be located in {htmlDocument.Source.Text}.");
+            return htmlDocument.RetrieveAntiforgeryToken();
         }
 
         public static CookieMetadata RetrieveAntiforgeryCookie(HttpResponseMessage response)

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

@@ -566,7 +566,7 @@ Products: Music Systems, Televisions (3)";
             var document = await Client.GetHtmlDocumentAsync(url);
 
             // Assert
-            var banner = QuerySelector(document, ".banner");
+            var banner = document.RequiredQuerySelector(".banner");
             Assert.Equal("Some status message", banner.TextContent);
         }
 
@@ -581,21 +581,10 @@ Products: Music Systems, Televisions (3)";
             var document = await Client.GetHtmlDocumentAsync(url);
 
             // Assert
-            var banner = QuerySelector(document, ".banner");
+            var banner = document.RequiredQuerySelector(".banner");
             Assert.Empty(banner.TextContent);
         }
 
-        private static IElement QuerySelector(IHtmlDocument document, string selector)
-        {
-            var element = document.QuerySelector(selector);
-            if (element == null)
-            {
-                throw new ArgumentException($"Document does not contain element that matches the selector {selector}: " + Environment.NewLine + document.DocumentElement.OuterHtml);
-            }
-
-            return element;
-        }
-
         private static HttpRequestMessage RequestWithLocale(string url, string locale)
         {
             var request = new HttpRequestMessage(HttpMethod.Get, url);

test/Microsoft.AspNetCore.Mvc.FunctionalTests/Infrastructure/IHtmlDocumentExtensions.cs

@@ -0,0 +1,43 @@
+// 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 AngleSharp.Dom;
+using AngleSharp.Dom.Html;
+
+namespace Microsoft.AspNetCore.Mvc.FunctionalTests
+{
+    public static class IHtmlDocumentExtensions
+    {
+        public static IElement RequiredQuerySelector(this IHtmlDocument document, string selector)
+        {
+            var element = document.QuerySelector(selector);
+            if (element == null)
+            {
+                throw new ArgumentException($"Document does not contain element that matches the selector {selector}: " + Environment.NewLine + document.DocumentElement.OuterHtml);
+            }
+
+            return element;
+        }
+
+        public static string RetrieveAntiforgeryToken(this IHtmlDocument htmlDocument)
+        {
+            var hiddenInputs = htmlDocument.QuerySelectorAll("form input[type=hidden]");
+            foreach (var input in hiddenInputs)
+            {
+                if (!input.HasAttribute("name"))
+                {
+                    continue;
+                }
+
+                var name = input.GetAttribute("name");
+                if (name == "__RequestVerificationToken" || name == "HtmlEncode[[__RequestVerificationToken]]")
+                {
+                    return input.GetAttribute("value");
+                }
+            }
+
+            throw new Exception($"Antiforgery token could not be located in {htmlDocument.Source.Text}.");
+        }
+    }
+}

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

@@ -11,7 +11,6 @@ using System.Net.Http.Headers;
 using System.Reflection;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting;
-using Microsoft.AspNetCore.Mvc.Authorization;
 using Microsoft.AspNetCore.Mvc.Filters;
 using Microsoft.AspNetCore.Testing;
 using Newtonsoft.Json.Linq;
@@ -144,6 +143,26 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
             Assert.Equal("CustomActionResult", content);
         }
 
+        [Fact]
+        public async Task Page_Handler_ReturnPartialWithoutModel()
+        {
+            // Act
+            var document = await Client.GetHtmlDocumentAsync("RenderPartialWithoutModel");
+
+            var element = document.RequiredQuerySelector("#content");
+            Assert.Equal("Welcome, Guest", element.TextContent);
+        }
+
+        [Fact]
+        public async Task Page_Handler_ReturnPartialWithModel()
+        {
+            // Act
+            var document = await Client.GetHtmlDocumentAsync("RenderPartialWithModel");
+
+            var element = document.RequiredQuerySelector("#content");
+            Assert.Equal("Welcome, Admin", element.TextContent);
+        }
+
         [Fact]
         public async Task Page_Handler_AsyncReturnTypeImplementsIActionResult()
         {

test/Microsoft.AspNetCore.Mvc.RazorPages.Test/PageModelTest.cs

@@ -1894,6 +1894,52 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages
             testPageModel.Verify();
         }
 
+        [Fact]
+        public void PartialView_WithName()
+        {
+            // Arrange
+            var viewData = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary());
+            var pageModel = new TestPageModel
+            {
+                PageContext = new PageContext
+                {
+                    ViewData = viewData
+                }
+            };
+
+            // Act
+            var result = pageModel.Partial("LoginStatus");
+
+            // Assert
+            Assert.NotNull(result);
+            Assert.Equal("LoginStatus", result.ViewName);
+            Assert.Same(viewData, result.ViewData);
+        }
+
+        [Fact]
+        public void PartialView_WithNameAndModel()
+        {
+            // Arrange
+            var viewData = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary());
+            var pageModel = new TestPageModel
+            {
+                PageContext = new PageContext
+                {
+                    ViewData = viewData
+                }
+            };
+            var model = new { Username = "Admin" };
+
+            // Act
+            var result = pageModel.Partial("LoginStatus", model);
+
+            // Assert
+            Assert.NotNull(result);
+            Assert.Equal("LoginStatus", result.ViewName);
+            Assert.Equal(model, result.Model);
+            Assert.Same(viewData, result.ViewData);
+        }
+
         [Fact]
         public void ViewComponent_WithName()
         {

test/Microsoft.AspNetCore.Mvc.RazorPages.Test/PageTest.cs

@@ -1697,6 +1697,52 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages
             Assert.Equal(statusCode, result.StatusCode);
         }
 
+        [Fact]
+        public void PartialView_WithName()
+        {
+            // Arrange
+            var viewData = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary());
+            var pageModel = new TestPage
+            {
+                ViewContext = new ViewContext
+                {
+                    ViewData = viewData
+                }
+            };
+
+            // Act
+            var result = pageModel.Partial("LoginStatus");
+
+            // Assert
+            Assert.NotNull(result);
+            Assert.Equal("LoginStatus", result.ViewName);
+            Assert.Same(viewData, result.ViewData);
+        }
+
+        [Fact]
+        public void PartialView_WithNameAndModel()
+        {
+            // Arrange
+            var viewData = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary());
+            var pageModel = new TestPage
+            {
+                ViewContext = new ViewContext
+                {
+                    ViewData = viewData
+                }
+            };
+            var model = new { Username = "Admin" };
+
+            // Act
+            var result = pageModel.Partial("LoginStatus", model);
+
+            // Assert
+            Assert.NotNull(result);
+            Assert.Equal("LoginStatus", result.ViewName);
+            Assert.Equal(model, result.Model);
+            Assert.Same(viewData, result.ViewData);
+        }
+
         [Fact]
         public void ViewComponent_WithName()
         {

test/WebSites/RazorPagesWebSite/RenderPartialWithModel.cs

@@ -0,0 +1,15 @@
+// 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;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+
+namespace RazorPagesWebSite
+{
+    public class RenderPartialWithModel : PageModel
+    {
+        public IActionResult OnGet() => Partial("_PartialWithModel", this);
+
+        public string Username => "Admin";
+    }
+}

test/WebSites/RazorPagesWebSite/RenderPartialWithModel.cshtml

@@ -0,0 +1,4 @@
+@page
+@model RazorPagesWebSite.RenderPartialWithModel
+
+<p>The partial will be loaded here ...</p>

test/WebSites/RazorPagesWebSite/RenderPartialWithoutModel.cshtml

@@ -0,0 +1,5 @@
+@page
+
+@functions {
+    public IActionResult OnGet() => Partial("_PartialWithoutModel");
+}

test/WebSites/RazorPagesWebSite/Views/Shared/_PartialWithModel.cshtml

@@ -0,0 +1,3 @@
+@model RazorPagesWebSite.RenderPartialWithModel
+
+<span id="content">Welcome, @Model.Username</span>

test/WebSites/RazorPagesWebSite/Views/Shared/_PartialWithoutModel.cshtml

@@ -0,0 +1 @@
+<span id="content">Welcome, Guest</span>