Hi Stef,
Thanks for your reply.
I checked the RenderBegin event call only once and the viewer's Report property only once but still the method (objectdatasource) for generation data in report called twice or sometime thrice.
Now I just changed in my implementation from objectdatasource to Report NeedDataSource it solved my problem. But I am still in curiosity about 2/3 times method call with objectdatasource problem.
Thanks
Chandan