The path you supply to UploadAsync should be the remote path in Dropbox where you want to put the uplaoded file content. It needs to match the regex pattern given in order to be a valid path for Dropbox.
The path you're currently supplying probably looks something like "C:\FolderName/\temp.dat". If you want to upload to a file in Dropbox named "file.dat" in a folder with name "FolderName", for example, you should supply a path like "/FolderName/file.dat".
We love to learn from the educators who use Dropbox. Whether you teach kids, teens, adults or a combination of all three, we want to know what apps and integrations you use with Dropbox to help with teaching. Which of the ones below is your favorite, or most used tool?