Recent changes made to the C# sdk (version 3.x) are causing some file upload issues.
The changes made to the official c# sdk recently are creating some issues while uploading files, corrupting them.
I bielive the DefaultHttpClient is in cause (on my solution i made change to override the method
Resquest1 to revert it to its previous behaviour).
Could you have a look at the issue : https://github.com/smartsheet/smartsheet-csharp-sdk/issues/51 .