System.Net.FtpWebRequest.EndGetRequestStream C# (CSharp) Method

        public override Stream EndGetRequestStream(IAsyncResult asyncResult)
        {
            if (NetEventSource.IsEnabled) NetEventSource.Enter(this);
            Stream requestStream = null;
            try
            {
                if (asyncResult == null)
                {
                    throw new ArgumentNullException(nameof(asyncResult));
                }

                LazyAsyncResult castedAsyncResult = asyncResult as LazyAsyncResult;

                if (castedAsyncResult == null)
                {
                    throw new ArgumentException(SR.net_io_invalidasyncresult, nameof(asyncResult));
                }

                if (castedAsyncResult.EndCalled)
                {
                    throw new InvalidOperationException(SR.Format(SR.net_io_invalidendcall, "EndGetResponse"));
                }

                castedAsyncResult.InternalWaitForCompletion();
                castedAsyncResult.EndCalled = true;
                CheckError();
                requestStream = _stream;
                castedAsyncResult.EndCalled = true;

                if (requestStream.CanTimeout)
                {
                    requestStream.WriteTimeout = ReadWriteTimeout;
                    requestStream.ReadTimeout = ReadWriteTimeout;
                }
            }
            catch (Exception exception)
            {
                if (NetEventSource.IsEnabled) NetEventSource.Error(this, exception);
                throw;
            }
            finally
            {
                if (NetEventSource.IsEnabled) NetEventSource.Exit(this);
            }
            return requestStream;
        }