System.Net.HttpRequestStream.EndRead C# (CSharp) Method

        public override int EndRead(IAsyncResult asyncResult)
        {
            if (NetEventSource.IsEnabled)
            {
                NetEventSource.Enter(this);
                NetEventSource.Info(this, $"asyncResult: {asyncResult}");
            }
            if (asyncResult == null)
            {
                throw new ArgumentNullException(nameof(asyncResult));
            }
            HttpRequestStreamAsyncResult castedAsyncResult = asyncResult as HttpRequestStreamAsyncResult;
            if (castedAsyncResult == null || castedAsyncResult.AsyncObject != this)
            {
                throw new ArgumentException(SR.net_io_invalidasyncresult, nameof(asyncResult));
            }
            if (castedAsyncResult.EndCalled)
            {
                throw new InvalidOperationException(SR.Format(SR.net_io_invalidendcall, nameof(EndRead)));
            }
            castedAsyncResult.EndCalled = true;
            // wait & then check for errors
            object returnValue = castedAsyncResult.InternalWaitForCompletion();
            Exception exception = returnValue as Exception;
            if (exception != null)
            {
                if (NetEventSource.IsEnabled)
                {
                    NetEventSource.Info(this, "Rethrowing exception:" + exception);
                    NetEventSource.Error(this, exception.ToString());
                }
                throw exception;
            }

            uint dataRead = (uint)returnValue;
            UpdateAfterRead((uint)castedAsyncResult.ErrorCode, dataRead);
            if (NetEventSource.IsEnabled)
            {
                NetEventSource.Info(this, $"returnValue:{returnValue}");
                NetEventSource.Exit(this);
            }

            return (int)dataRead + (int)castedAsyncResult._dataAlreadyRead;
        }