How to detect that a file was successfully received by a web client?

My question is similar to this post but I have to do the same using IIS, ASP.NET, and C#.

None of the methods in the HttpResponse class provide feedback if the data was sent or not, Transm开发者_如何学CitFile() just does its job (or not) and does not provide any means of knowing the result.

I was thinking of using the .Filter property but then again, the filter is based on the HttpResponseStream which does also not provide any feedback.

Any ideas?

After some testing I came up with the following solution to the problem. TransmitFile() has one serious limitation: it reads the whole file into memory before sending, this is really bad for larger files. So basically I resorted to manual chunking and checking if the client is connected after each chunk.

context.Response.Clear();
context.Response.BufferOutput = false;
context.Response.ContentType = "application/octet-stream";
context.Response.AddHeader("Content-Disposition", "attachment; filename=" + originalFilename);
context.Response.AddHeader("Content-Length", fileLength.ToString());
context.Response.Cache.SetNoStore();

context.Response.Flush();

downloadFailed = !context.Response.IsClientConnected;

int thisChunk;
long offset = 0;
int chunkSize = 1024 * 8;
byte[] bytes = new byte[chunkSize];

FileStream r = File.OpenRead(localFilename);

while((offset < fileLength) && !downloadFailed)
{
    if((fileLength - offset) < chunkSize)
    {
        thisChunk = (int)(fileLength - offset);
    }
    else
    {
        thisChunk = chunkSize;
    }

    r.Read(bytes, 0, chunkSize);

    try
    {
        context.Response.BinaryWrite(bytes);
        context.Response.Flush();

        if(!context.Response.IsClientConnected)
        {
            downloadFailed = true;
        }
    }
    catch(ObjectDisposedException ex1)
    {
        // Stream is closed, nothing written
        break;
    }
    catch(System.IO.IOException ex3)
    {
        // I/O error, unknown state, abort
        Trace.Write(ex3);
        break;
    }

    offset += thisChunk;
}

if(!downloadFailed)
{
    // now update the file, statistics, etc
}

context.Response.Flush();

HttpContext.Current.ApplicationInstance.CompleteRequest();

Will need to play a bit with the chunk size to find the optimal size. But basically it works reliably like this.

Check Response.IsClientConnected after calling TransmitFile.