How to filter request in a webapi core

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C#

.NET

WebAPI

Hello all,

so im trying to filter que requests to an api, to process some filed in the header, i used ,mapwhen(), i can filter do what i want but then the process doesn continue, basicaly return nothing it doesnt go to the controller.

what i am missing?

What I have tried:

app.MapWhen(context => 
context.Request.Headers.ContainsKey("value"),
                (appbuilder) =>
                    {
                    //appbuilder.Run(async (context) =>  { await context.Response.WriteAsync("Tinha ano"); });
                    appbuilder.Use(async (context, next) =>
                    {
                        Microsoft.Extensions.Primitives.StringValues value;

                        context.Request.Headers.TryGetValue("value", out value);
                                               

                        if (vaue != "5")
                        {
                            await Task.FromResult(context.Response.StatusCode = StatusCodes.Status406NotAcceptable);
                        }