RequestStream rewrite

gistfile1.cs

        public RequestStream(Stream stream, long expectedLength, long thresholdLength, bool disableStreamSwitching)
        {
            this.thresholdLength = thresholdLength;
            this.disableStreamSwitching = disableStreamSwitching;
            this.stream = stream ?? this.CreateDefaultMemoryStream(expectedLength);

            ThrowExceptionIfCtorParametersWereInvalid(this.stream, expectedLength, this.thresholdLength);

            if (!this.MoveStreamOutOfMemoryIfExpectedLengthExceedExpectedLength(expectedLength))
            {
                this.MoveStreamOutOfMemoryIfContentsLengthExceedThresholdAndSwitchingIsEnabled();
            }

            if (!this.stream.CanSeek)
            {
                var task =
                    MoveToWritableStream();
 
                task.Wait();
  
                if (task.IsFaulted)
                {
                   throw new InvalidOperationException("Unable to copy stream", task.Exception);
                }

                this.stream = task.Result;
            }

            this.stream.Position = 0;
        }

        private Task<Stream> MoveToWritableStream()
        {
            var tcs = new TaskCompletionSource<Stream>();

            var buffer =
                new MemoryStream((int)this.stream.Length);

            this.stream.CopyTo(buffer, (source, destination, ex) =>
            {
                if (ex != null)
                {
                    tcs.SetException(ex);
                }
                else
                {
                    tcs.SetResult(destination);
                }
            });

            return tcs.Task;
        }