Is there Any way to set informations in my owncloud calendar by using my own C# client?
In web i just find informations how to read stuff from the calendar.
You find all needed information on the net how to write and read from a CalDAV server like ownCloud is. Starting points are a short research on the net or on pages like:
https://devguide-calconnect.rhcloud.com/CalDAV-introduction
P.S. Wrong category chosen here as the desktop sync client is not speaking CalDAV.