Thank you for writing.
We have an example of drag and drop between two instances of RadGridView in our Demo Application >
RadGridView > Rows > Rows Drag & Drop. Please take a look at the example. In the demo you can also see its implementation. Please note that RadGridView supports drag and drop only in unbound mode.
If you are using bound mode, you should use the example provided by our MVP here: http://www.telerik.com/community/code-library/winforms/gridview/drag-and-drop-in-bound-mode.aspx
I hope this helps.
the Telerik team