Published 30-Mar-17 How to Add / Remove Site Collection Administrator in SharePoint Office 365 Programmatically using C# Client Site Object Model (CSOM) In the previous article, we saw how to add a User as Site Collection administrator in SharePoint Office 365. But, it requires a Tenant Admin User Credentials. But, most of the cases, we may not get that for all the customers. Hence, thought of coming up with an approach with Site Collection Permission itself. The below code is self-explanatory.