Simple way to calculate Response length in MVC4

I was trying to calculate the length of a HTTP Response.
Seems the stream doesn’t want to play. (no read allowed. and the Content-Length doesn’t seem set)
I was hoping to simply call some length property on the HttpContent response.
I have since googled and seen what looks to me like convoluted solutions around filters which I don’t understand.
Is it possible to access the length (content itself is option extra )
If not I would appreciate a link to an example for ‘mvc4/.net 4.5 filter’ included
that I should work though till I do understand. 🙂

   public override void Init()
    {
        base.Init();
        EndRequest += new EventHandler(EndRequestHandler);
    }
    public void EndRequestHandler(object sender, EventArgs e) {
        var     admService = new AdminServices();
        admService.HTTPTrace(Context);
    }


 public void HTTPTrace(HttpContext httpContext) {
        try {
            var eventTrace = new MasterEventTrace();
            eventTrace.RemoteAddress = req.UserHostAddress;
            eventTrace.RequestLengthBytes = req.ContentLength;

          //  var targetMemoryStream = new MemoryStream();
          //   res.OutputStream.CopyTo(targetMemoryStream);
            int len;
            int.TryParse(res.Headers["Content-Length"], out len );
            eventTrace.StatusCode = res.StatusCode;
            eventTrace.ResponseLengthBytes = len;    // <<<<<<< HOW to calculate this

EDIT: Based on Darin’s response I got this working, Thank You Darin
I made a few tweaks to suit the situation, but otherwise as suggested.
It shows a little more from Global.asax.cs, and logging the Request and Response info as required.

//Global.asax.cs
  public override void Init()        {
        base.Init();
        BeginRequest += new EventHandler(BeginRequestHandler);
        EndRequest += new EventHandler(EndRequestHandler);
    }

   public void EndRequestHandler(object sender, EventArgs e)
    {
        var adminService = new AdminServices();
        var handler = Context.Response.Filter as ResponseStreamHandler;
        adminService.HTTPTrace(Context, handler);
    }

    public void BeginRequestHandler(object sender, EventArgs e)
    {
        BootStrapUnauthentiated();
        Context.Response.Filter = new ResponseStreamHandler(Context.Response.Filter);
    }

 public void HTTPTrace(HttpContext httpContext, ResponseStreamHandler responseStreamFilter)
    {
        try {
            var _ILuwMaster = BosGlobal.BGA.ILuwMaster();

            var req = httpContext.Request;
            var res = httpContext.Response;
            var eventTrace = new MasterEventTrace();
            eventTrace.EventName =  req.RequestType  +":"+ req.Url.LocalPath;
            eventTrace.EventDateTime = BosGlobal.BGA.Calendar.Now;
            eventTrace.RemoteAddress = req.UserHostAddress;
            eventTrace.RequestLengthBytes = req.ContentLength;
            eventTrace.ResponseLengthBytes = responseStreamFilter.ResponseSize;   //<<<<<<HERE
            eventTrace.StatusCode = res.StatusCode;
            // save trace entry in DB
            _ILuwMaster.GetRepository<MasterEventTrace>().Add(eventTrace);
            _ILuwMaster.Commit();
        }
        catch (Exception ex ) {} // DONT KILL Live traffic when logging errors occur
    }

 public class ResponseStreamHandler : MemoryStream {
    private readonly Stream _responseStream;
    public long ResponseSize { get; private set; } 
    public ResponseStreamHandler(Stream responseStream) {
        this._responseStream = responseStream;
        ResponseSize = 0;
    }

    public override void Write(byte[] buffer, int offset, int count) {
        this.ResponseSize += count;
        this._responseStream.Write(buffer, offset, count);
    }

    public override void Flush() {
      base.Flush();
    }
}

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

You could write a custom Response filter:

public class ResponseLengthCalculatingStream: MemoryStream
{
    private readonly Stream responseStream;
    private long responseSize = 0;
    public ResponseLengthCalculatingStream(Stream responseStream)
    {
        this.responseStream = responseStream;
    }

    public override void Write(byte[] buffer, int offset, int count)
    {
        this.responseSize += count;
        this.responseStream.Write(buffer, offset, count);
    }

    public override void Flush()
    {
        var responseSize = this.responseSize;
        // Here you know the size of the response ...
        base.Flush();
    }
}

and register it in your Global.asax:

protected void Application_BeginRequest()
{
    Context.Response.Filter = new ResponseLengthCalculatingStream(Context.Response.Filter);
}

And if you wanted to apply this filter only on particular controller actions you could write a custom action filter instead of applying it in the BeginRequest event in Global.asax:

public class ResponseLengthCapturingAttribute: ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        var response = filterContext.HttpContext.Response;
        response.Filter = new ResponseLengthCalculatingStream(response.Filter);
    }
}

and then all that’s left is decorate the controller action with the corresponding action filter:

[ResponseLengthCapturing]
public ActionResult Index()
{
    ...
    return View();
}

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0