weiyilai · pull · Dec 17, 2025 · Dec 17, 2025 · Dec 17, 2025
diff --git a/src/Components/Web.JS/src/Rendering/Events/EventTypes.ts b/src/Components/Web.JS/src/Rendering/Events/EventTypes.ts
@@ -23,6 +23,12 @@ export function registerCustomEventType(eventName: string, options: EventTypeOpt
     throw new Error(`The event '${eventName}' is already registered.`);
   }
 
+  // When aliasing a browser event, the custom event name must be different from the browser event name
+  // to avoid double-triggering (once for the browser event, once for the custom event wrapper)
+  if (options.browserEventName && eventName === options.browserEventName) {
+    throw new Error(`The custom event '${eventName}' cannot have the same name as its browserEventName '${options.browserEventName}'. Choose a different name for the custom event.`);
+  }
+
   // If applicable, register this as an alias of the given browserEventName
   if (options.browserEventName) {
     const aliasGroup = browserEventNamesToAliases.get(options.browserEventName);

diff --git a/src/Components/test/E2ETest/Tests/EventCustomArgsTest.cs b/src/Components/test/E2ETest/Tests/EventCustomArgsTest.cs
@@ -170,6 +170,17 @@ public void CanRegisterCustomEventAndSupplyComplexParams()
             line => Assert.Equal("Event with IJSObjectReference received: Hello!", line));
     }
 
+    [Fact]
+    public void ThrowsErrorWhenEventNameMatchesBrowserEventName()
+    {
+        // Attempt to register a custom event with the same name as the browser event
+        Browser.Exists(By.Id("register-invalid-same-name-event")).Click();
+
+        // Verify that an error is thrown
+        var errorMessage = Browser.Exists(By.Id("same-name-event-error")).Text;
+        Assert.Contains("cannot have the same name as its browserEventName", errorMessage);
+    }
+
     void SendKeysSequentially(IWebElement target, string text)
     {
         foreach (var c in text)

diff --git a/src/Components/test/testassets/BasicTestApp/EventCustomArgsComponent.razor b/src/Components/test/testassets/BasicTestApp/EventCustomArgsComponent.razor
@@ -60,6 +60,15 @@
             onclick="Blazor.registerCustomEventType('custommouseover', { browserEventName: 'mouseover' })">
         Register custom mouseover event (which has no corresponding native listener)
     </button>
+
+    <button id="register-invalid-same-name-event"
+            onclick="try { Blazor.registerCustomEventType('scrolltop', { browserEventName: 'scrolltop' }); document.getElementById('same-name-event-error').textContent = 'No error thrown'; } catch (error) { document.getElementById('same-name-event-error').textContent = error.message; }">
+        Try to register event with same name as browserEventName (should throw error)
+    </button>
+</p>
+
+<p>
+    <span id="same-name-event-error"></span>
 </p>
 
 <p>

diff --git a/src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs b/src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs
@@ -16,6 +16,7 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyModel;
 using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Options;
 
 namespace Microsoft.AspNetCore.Mvc.Testing;
 
@@ -588,7 +589,16 @@ private static void EnsureDepsFile()
     /// </summary>
     /// <param name="serviceProvider">The <see cref="IServiceProvider"/> from the bootstrapped application.</param>
     /// <returns></returns>
-    protected virtual TestServer CreateServer(IServiceProvider serviceProvider) => new(serviceProvider);
+    protected virtual TestServer CreateServer(IServiceProvider serviceProvider)
+    {
+        var options = serviceProvider.GetService<IOptions<TestServerOptions>>();
+        if (options is not null)
+        {
+            return new(serviceProvider, options);
+        }
+
+        return new(serviceProvider);
+    }
 
     /// <summary>
     /// Creates the <see cref="IHost"/> with the bootstrapped application in <paramref name="builder"/>.

diff --git a/src/Mvc/test/Mvc.FunctionalTests/TestServerWithCustomConfigurationIntegrationTests.cs b/src/Mvc/test/Mvc.FunctionalTests/TestServerWithCustomConfigurationIntegrationTests.cs
@@ -0,0 +1,56 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Net;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Mvc.Testing;
+using Microsoft.AspNetCore.TestHost;
+
+namespace Microsoft.AspNetCore.Mvc.FunctionalTests;
+
+public class CustomWebApplicationFactory : WebApplicationFactory<SimpleWebSite.Startup>
+{
+    public Action<TestServerOptions> ConfigureOptions { get; set; }
+
+    protected override void ConfigureWebHost(IWebHostBuilder builder)
+    {
+        builder.UseTestServer(ConfigureOptions);
+    }
+}
+
+public class TestServerWithCustomConfigurationIntegrationTests : IClassFixture<CustomWebApplicationFactory>
+{
+    public CustomWebApplicationFactory Factory { get; }
+
+    public TestServerWithCustomConfigurationIntegrationTests(CustomWebApplicationFactory factory)
+    {
+        Factory = factory;
+    }
+
+    [Fact]
+    public async Task ServerConfigured()
+    {
+        // Arrange
+        var optionsConfiguredCounter = 0;
+        Factory.ConfigureOptions = options =>
+        {
+            options.AllowSynchronousIO = true;
+            options.PreserveExecutionContext = true;
+            optionsConfiguredCounter++;
+        };
+
+        // Act
+        Assert.Equal(0, optionsConfiguredCounter);
+        Factory.StartServer();
+
+        using var client = Factory.CreateClient();
+
+        using var response = await client.GetAsync("/");
+
+        // Assert
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal(1, optionsConfiguredCounter);
+        Assert.True(Factory.Server.AllowSynchronousIO);
+        Assert.True(Factory.Server.PreserveExecutionContext);
+    }
+}