HttpWebRequest.GetRequestStream : What it does?

Question

Code exemple:

HttpWebRequest request =
   (HttpWebRequest)HttpWebRequest.Create(\"http://some.existing.url\");

request.Method = \"POST\";
request.ContentType          


        

Answer 1

You use GetRequestStream() to synchronously obtain a reference to the upload stream. It is only after you have finished writing to the stream that the actual request is send.

However, I would suggest that you use the BeginGetRequestStream method instead of GetRequestStream. BeginGetRequestStream performs asynchronously and don't lock the current thread while the stream is being obtained. You pass a callback and a context to the BeginGetRequestStream. In the callback, you can call EndGetRequestStream() to finally grab a reference and repeat the writing steps listed above (for synchronous behavior). Example:

context.Request.BeginGetRequestStream(new AsyncCallback(Foo), context);

public void Foo(IAsyncResult asyncResult)
    {
        Context context = (Context)asyncResult.AsyncState;
        try
        {
            HttpWebRequest request = context.Request;

            using (var requestStream = request.EndGetRequestStream(asyncResult))
            using (var writer = new StreamWriter(requestStream))
            {
                // write to the request stream
            }

            request.BeginGetResponse(new AsyncCallback(ProcessResponse), context);
        }

Be very careful with BeginGetRequestStream. It never times out, thus you must add additional logic to your program to recover from situations where GetRequestStream will throw a timeout exception.

In general, threads are cheap. The async Begin/End methods of HttpWebRequest are only worth using if you will have 10,000 or more concurrent requests; because implementing timeouts is very tricky and error-prone. In general, using BeginGetRequestStream is premature optimization unless you need significant performance gains.