c＃-流的意外结束，该内容可能已被另一个组件读取

Question

I've been trying to get this to work, but no luck.

I have middleware class where used to verify uploaded files.

After middleware debug goes to the Controller class, but not to the action. Context Request ending after controller's constructor.

Middleware class:

 public class UploadMiddleware
{

    public UploadMiddleware(RequestDelegate next)
    {
        _next = next;
    }

        [DisableFormValueModelBinding]
        [ValidateAntiForgeryToken]
    public async Task Invoke(HttpContext context)
    {
        var authToken = context.Request.Headers["id"].ToString();
        var path = context.Request.Path.ToString();
        var streamBody = context.Request.Body;

            if (authToken != String.Empty)
            {
                if (!IsMultipartContentType(context.Request.ContentType))
                {
                    await context.Response.WriteAsync("Unexpected error.");  
                    await _next(context);              
                    return;
                }

                var boundary = GetBoundary(context.Request.ContentType); 
                var reader = new MultipartReader(boundary, context.Request.Body);
                // reader.HeadersLengthLimit = int.MaxValue;
                // reader.BodyLengthLimit = long.MaxValue;

                var section = await reader.ReadNextSectionAsync();
                var buffer = new byte[256];
                while (section != null)
                {
                    var fileName = GetFileName(section.ContentDisposition);
                    var bytesRead = 0;

                    using (var stream = new FileStream(fileName,FileMode.Append))
                    {                                         
                        do{

                            bytesRead = await section.Body.ReadAsync(buffer, 0, buffer.Length);
                            stream.Write(buffer, 0, bytesRead);       
                             buffer = Convert.FromBase64String(System.Text.Encoding.UTF8.GetString(buffer));
                       } while (bytesRead < 0);                   
                    }


                    if (!verifyUpcomingFiles(buffer))
                    {
                        await context.Response.WriteAsync("Undefined file type detected.");
                        return;
                    }
                     else
                     {
                      context.Request.Headers.Add("isVerified","verified");                                                    
                    }


                     section = await reader.ReadNextSectionAsync();      
                }


            }
            else
            {
                await context.Response.WriteAsync("You are not allowed to complete this process.");
                return;

            }
            await _next(context);


    }

I am stuck in this problem. I really need someone point me in a direction, that would be greatly appreciated.

Answer 1

The error message is pretty clear, as well as the docs are and warns you about it in big red box :

Warning

Do not call next.Invoke after the response has been sent to the client. Changes to HttpResponse after the response has started will throw an exception. For example, changes such as setting headers, status code, etc, will throw an exception. Writing to the response body after calling next :

• May cause a protocol violation. For example, writing more than the stated content-length.

• May corrupt the body format. For example, writing an HTML footer to a CSS file.

HttpResponse.HasStarted is a useful hint to indicate if headers have been sent and/or the body has been written to.

if (!IsMultipartContentType(context.Request.ContentType))
{
    await context.Response.WriteAsync("Unexpected error.");  
    // Here you're calling the next middleware after writing to the response stream!
    await _next(context);              
    return;
}