In the GridView to use DataTable to use CustomAggregateFunction???

[Guntae Park]

Hi

i bind DataTable to GridView.
and then i used CustomAggregateFunction(StandardDeviationFunction)...

then occur Exception : 
InvalidOperationException.
No generic method 'StdDev' on type 'RadGridViewTest.Statistics' is compatible with the supplied type arguments and arguments. No type arguments should be provided if the method is non-generic.

how to do i????

thank you