We all at some time struggled with uploading large files using CSOM in O365. Using managed client object model, we can upload a maximum of 2MB file size. If the file is of larger size, we usually had two options:
The first option can not be used in Sharepoint Online because SaveBinaryDirect does not work with claims authentication (check this link). Does that mean we are left with REST only? Actually NO. We have one more way by which we can upload files greater than 2MB in O365 using CSOM in provider hosted app. But let’s first see the standard CSOM way which allows us 2MB file upload.
Now the method to upload larger files is exactly the same. We only have to use FileCreationInformation.ContentStream property instead of FileCreationInformation.Content property. The whole code is present below:
In some cases, you might get a FileNotFoundException while using above code. Below is another way to use the code
Note that I replaced FileStream with the input stream present in the uploaded file itself.
P.S. I have tested the above code for files upto 50 MB. It depends largely on internet speed. Once for 50MB file size it gave me time out error (which could be fixed by setting RequestTimeout property of client context)
Hope this helps.