FormAction from QueryString

src/Microsoft.AspNetCore.Mvc.RazorPages/Internal/DefaultPageHandlerMethodSelector.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using Microsoft.Extensions.Primitives;
 
 namespace Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure
 {
@@ -65,6 +66,13 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure
             List<HandlerMethodDescriptor> handlersToConsider = null;
 
             var formAction = Convert.ToString(context.RouteData.Values[FormAction]);
+
+            if (string.IsNullOrEmpty(formAction) &&
+                context.HttpContext.Request.Query.TryGetValue(FormAction, out StringValues queryValues))
+            {
+                formAction = queryValues[0];
+            }
+
             for (var i = 0; i < handlers.Count; i++)
             {
                 var handler = handlers[i];

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

@@ -20,6 +20,26 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
 
         public HttpClient Client { get; }
 
+        [Fact]
+        public async Task Page_Handler_FormActionFromQueryString()
+        {
+            // Arrange & Act
+            var content = await Client.GetStringAsync("http://localhost/HandlerTestPage?formaction=Customer");
+
+            // Assert
+            Assert.StartsWith("Method: OnGetCustomer", content.Trim());
+        }
+
+        [Fact]
+        public async Task Page_Handler_FormActionRouteDataChosenOverQueryString()
+        {
+            // Arrange & Act
+            var content = await Client.GetStringAsync("http://localhost/HandlerTestPage/Customer?formaction=ViewCustomer");
+
+            // Assert
+            Assert.StartsWith("Method: OnGetCustomer", content.Trim());
+        }
+
         [Fact]
         public async Task Page_Handler_FormAction()
         {

test/Microsoft.AspNetCore.Mvc.RazorPages.Test/Internal/DefaultPageHandlerMethodSelectorTest.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Reflection;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure;
 using Microsoft.AspNetCore.Routing;
@@ -234,6 +233,147 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Internal
             Assert.Same(descriptor1, actual);
         }
 
+        [Fact]
+        public void Select_FormActionFromQueryString()
+        {
+            // Arrange
+            var descriptor1 = new HandlerMethodDescriptor
+            {
+                HttpMethod = "POST",
+                FormAction = new StringSegment("Add"),
+            };
+
+            var descriptor2 = new HandlerMethodDescriptor
+            {
+                HttpMethod = "POST",
+                FormAction = new StringSegment("Delete"),
+            };
+
+            var pageContext = new PageContext
+            {
+                ActionDescriptor = new CompiledPageActionDescriptor
+                {
+                    HandlerMethods =
+                    {
+                        descriptor1,
+                        descriptor2,
+                    },
+                },
+                RouteData = new RouteData(),
+                HttpContext = new DefaultHttpContext
+                {
+                    Request =
+                    {
+                        Method = "Post",
+                        QueryString = new QueryString("?formaction=Delete"),
+                    },
+                },
+            };
+            var selector = new DefaultPageHandlerMethodSelector();
+
+            // Act
+            var actual = selector.Select(pageContext);
+
+            // Assert
+            Assert.Same(descriptor2, actual);
+        }
+
+        [Fact]
+        public void Select_FormActionConsidersRouteDataFirst()
+        {
+            // Arrange
+            var descriptor1 = new HandlerMethodDescriptor
+            {
+                HttpMethod = "POST",
+                FormAction = new StringSegment("Add"),
+            };
+
+            var descriptor2 = new HandlerMethodDescriptor
+            {
+                HttpMethod = "POST",
+                FormAction = new StringSegment("Delete"),
+            };
+
+            var pageContext = new PageContext
+            {
+                ActionDescriptor = new CompiledPageActionDescriptor
+                {
+                    HandlerMethods =
+                    {
+                        descriptor1,
+                        descriptor2,
+                    },
+                },
+                RouteData = new RouteData
+                {
+                    Values =
+                    {
+                        { "formaction", "Add" }
+                    }
+                },
+                HttpContext = new DefaultHttpContext
+                {
+                    Request =
+                    {
+                        Method = "Post",
+                        QueryString = new QueryString("?formaction=Delete"),
+                    },
+                },
+            };
+            var selector = new DefaultPageHandlerMethodSelector();
+
+            // Act
+            var actual = selector.Select(pageContext);
+
+            // Assert
+            Assert.Same(descriptor1, actual);
+        }
+
+        [Fact]
+        public void Select_FormActionMultipleTimesInQueryString_UsesFirst()
+        {
+            // Arrange
+            var descriptor1 = new HandlerMethodDescriptor
+            {
+                HttpMethod = "POST",
+                FormAction = new StringSegment("Add"),
+            };
+
+            var descriptor2 = new HandlerMethodDescriptor
+            {
+                HttpMethod = "POST",
+                FormAction = new StringSegment("Delete"),
+            };
+
+            var pageContext = new PageContext
+            {
+                ActionDescriptor = new CompiledPageActionDescriptor
+                {
+                    HandlerMethods =
+                    {
+                        descriptor1,
+                        descriptor2,
+                    },
+                },
+                RouteData = new RouteData(),
+                HttpContext = new DefaultHttpContext
+                {
+                    Request =
+                    {
+                        Method = "Post",
+                        QueryString = new QueryString("?formaction=Delete&formaction=Add"),
+                    },
+                },
+            };
+            var selector = new DefaultPageHandlerMethodSelector();
+
+            // Act
+            var actual = selector.Select(pageContext);
+
+            // Assert
+            Assert.Same(descriptor2, actual);
+        }
+
         [Fact]
         public void Select_ReturnsHandlerWithMatchingHttpMethodWithoutAFormAction()
         {