c# - 解决错误 - "An item with the same key has already been added when returning 404"

Question

我的自定义错误页面处理程序定义如下:

if (env.IsDevelopment())
{
    app.UseDeveloperExceptionPage();
    app.UseBrowserLink();
}
else
{
    app.UseExceptionHandler("/Error");
}

app.UseStatusCodePagesWithReExecute("/Error/{0}");

app.UseMvc(routes =>
{
    ...
}

然后在错误 Controller 中:

public class ErrorController : Controller
{
    public IActionResult Index(int errorCode)
    {
        switch (errorCode)
        {
            case 404:
                return View($"~/Views/Error/{errorCode}.cshtml");
        }

        return View(errorCode);
    }
}

在生产模式下一切正常，但在开发模式下，有两种情况:

1. 我“就像那样”访问了 404 页面，它显示了我的自定义 404 页面(这是正确的)

2. 我正在强制执行 404 操作，例如。

   if(nothingFound)
   {
       return NotFound();
   }
   

   然后它进入 ErrorController 操作，甚至进入 View (404.cshtml)，但之后它打印整个调试标题:

ArgumentException: An item with the same key has already been added. Key: System.Object

使用 app.UseDeveloperExceptionPage() 时是否正常，还是我配置错误？

更新

堆栈跟踪:

System.ArgumentException: An item with the same key has already been added. Key: System.Object
   at System.ThrowHelper.ThrowAddingDuplicateWithKeyArgumentException(Object key)
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeNextResourceFilter>d__22.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ResourceExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeAsync>d__20.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Builder.RouterMiddleware.<Invoke>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware`1.<Invoke>d__18.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware`1.<Invoke>d__18.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Builder.StatusCodePagesExtensions.<>c__DisplayClass6_0.<<UseStatusCodePagesWithReExecute>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Diagnostics.StatusCodePagesMiddleware.<Invoke>d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Localization.RequestLocalizationMiddleware.<Invoke>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Web.BrowserLink.Runtime.BrowserLinkMiddleware.<ExecuteWithFilter>d__7.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.<Invoke>d__7.MoveNext()

Answer 1

我遇到了类似的问题。后来发现问题是跟中间件的使用顺序有关。我使用中间件编写响应 header ，例如 X-Content-Type-Options 和其他 header 。我只是将其移至 app.UseStatusCodePagesWithReExecute 上方，它开始正常工作。所以我当前的代码是这样的:

app.Use(async (context, next) =>
        {
            context.Response.Headers.Add("X-Content-Type-Options", "nosniff");
            context.Response.Headers.Add("X-Xss-Protection", "1");
            context.Response.Headers.Add("X-Frame-Options", "SAMEORIGIN");
            await next();
        });

        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
            app.UseDatabaseErrorPage();
            app.UseBrowserLink();
        }
        else
        {
            app.UseStatusCodePagesWithReExecute("/Home/Error/{0}");
        }

希望这可以帮助任何像我一样遇到类似问题的人。