Simple way to calculate Response length in MVC4 - asp.net

Question

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();
}
}

Answer 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();
}