当MVC 3不止一个​​时，缓慢流式传输图像

Question

I have a problem with streaming small images from database using EF5 and MVC3

It works great when I stream 1 picture out, but when a page contains like 5 of those pictures its like glue and they take up to 5 seconds to load eventhough each are only like 5-200kb large.

I read some post and added this to web.config

<system.net> 
  <connectionManagement> 
    <add address="*" maxconnection="100" /> 
  </connectionManagement> 
</system.net> 

It didnt have any effect on my issue.

And using this for streaming:

 public class ImageResult : ActionResult
    {
        public ImageResult(Stream imageStream, string contentType)
        {
            if (imageStream == null)
                throw new ArgumentNullException("imageStream");
            if (contentType == null)
                throw new ArgumentNullException("contentType");

            this.ImageStream = imageStream;
            this.ContentType = contentType;
        }

        public Stream ImageStream { get; private set; }
        public string ContentType { get; private set; }

        public override void ExecuteResult(ControllerContext context)
        {
            if (context == null)
                throw new ArgumentNullException("context");

            HttpResponseBase response = context.HttpContext.Response;

            response.ContentType = this.ContentType;

            byte[] buffer = new byte[4096];
            while (true)
            {
                int read = this.ImageStream.Read(buffer, 0, buffer.Length);
                if (read == 0)
                    break;

                response.OutputStream.Write(buffer, 0, read);
            }

            response.End();
        }
    }

UPDATE

I removed the ImageResult and added return File...... speeds things up, but still not acceptable speeds..... 2 seconds for 18kb file.

Controller:

   [SessionState(SessionStateBehavior.Disabled)]
   public class ContentController : Controller
    {
    .....
       public ActionResult Thumbnail(int fileID, int width)
       {
           var thumbnail = _fileRep.GetThumbnail(fileID, width);

           return File(thumbnail.FileContent, thumbnail.ContentType);
        }

Answer 1

Most probably the issue you are facing is caused by the fact that access to ASP.NET session state is exclusive per session. This means that if two concurrent requests are made for the same session (by using the same SessionID value), the first request gets exclusive access to the session information. The second request executes only after the first request is finished. You can read more about it here: ASP.NET Session State Overview ( Concurrent Requests and Session State section)

If your actions methods for the images doesn't require access to session, you can resolve your issue by decorating the controller with SessionStateAttribute attribute:

[SessionState(SessionStateBehavior.Disabled)]

This will allow the controller to handle the requests in "parallel" way.

In case when you need read access to session, you can try using the SessionStateBehavior.ReadOnly value. This will not result in an exclusive lock but the request will still have to wait for a lock set by a read-write request.