That scenario should be possible- it will just require a little code in your Content Page.
The process should basically be this:
- Handle your ContentPage's PageLoad event
- During that event, locate the RadGrid in your MasterPage (Master.FindControl("YourRadGridId") as RadGrid)
- Set the grid's DataSourceId property to the ID of your data source (myGrid.DataSourceID = mySqlDataSource.ID)
I don't have VS handy, but I'm fairly certain this should work. It should be early enough in the Page Lifecycle. Once the DataSourceId is set, the Grid will bind and behave "like normal."
Let me know if that helps.