c# - 从 ASP.NET Core 中的 WebSocket 请求返回什么 IActionResult？

Question

我有一个正在运行的 ASP.NET Core 2.1 webapi 正在监听网络套接字请求。如果请求不是针对 WebSocket 升级，我想返回 this.BadRequest()。

[Route("api/[controller]")]
[ApiController]
public class SocketController : ControllerBase
{
    [HttpGet]
    public async Task<IActionResult> Post()
    {
        if (!this.HttpContext.WebSockets.IsWebSocketRequest)
            return this.BadRequest();

        using (var webSocket = await this.HttpContext.WebSockets.AcceptWebSocketAsync())
        {
            using (var jsonRpc = new JsonRpc(new WebSocketMessageHandler(webSocket)))
            {
                jsonRpc.AddLocalRpcTarget(new SocketServer());
                jsonRpc.StartListening();
                await jsonRpc.Completion;
            }
        }

        return this.Ok();
    }
}

但是无论走成功路径还是失败路径，服务器都会抛出异常:

fail: Microsoft.AspNetCore.Server.Kestrel[13] Connection id "0HLEM87126JEO", Request id "0HLEM87126JEO:00000001": An unhandled exception was thrown by the application. System.InvalidOperationException: StatusCode cannot be set because the response has already started. at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.ThrowResponseAlreadyStartedException(String value) at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.set_StatusCode(Int32 value) at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.Microsoft.AspNetCore.Http.Features.IHttpResponseFeature.set_StatusCode(Int32 value) at Microsoft.AspNetCore.Http.Internal.DefaultHttpResponse.set_StatusCode(Int32 value) at Microsoft.AspNetCore.Mvc.StatusCodeResult.ExecuteResult(ActionContext context) at Microsoft.AspNetCore.Mvc.ActionResult.ExecuteResultAsync(ActionContext context) at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeResultAsync(IActionResult result) at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResultFilterAsyncTFilter,TFilterAsync at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResultExecutedContext context) at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeResultFilters() at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResourceFilter() at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context) at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeFilterPipelineAsync() at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeAsync() at Microsoft.AspNetCore.Builder.RouterMiddleware.Invoke(HttpContext httpContext) at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context) at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context) at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.ProcessRequests[TContext](IHttpApplication`1 application)

如果我将方法更改为只返回 Task 就可以正常工作，这样我就不必提供 IActionResult，但是我没有办法对错误请求返回 400 响应。解决此问题的最佳方法是什么？

我的中间件非常简单:

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            // app.UseHsts();
        }

        // app.UseHttpsRedirection();
        app.UseWebSockets();
        app.UseMvc();
    }

Answer 1

secret 是 EmptyResult，它没有 this.Empty() 方法。

public async Task<IActionResult> Post()
{
    if (!this.HttpContext.WebSockets.IsWebSocketRequest)
    {
        return this.BadRequest();
    }

    using (var webSocket = await this.HttpContext.WebSockets.AcceptWebSocketAsync())
    {
        using (var jsonRpc = new JsonRpc(new WebSocketMessageHandler(webSocket)))
        {
            jsonRpc.AddLocalRpcTarget(new SocketServer());
            jsonRpc.StartListening();
            await jsonRpc.Completion;
        }
    }

    return new EmptyResult();
}