RadGridView Sort Operation in Wpf

Question

hi,

when i apply this Property for RadGridView,


            <Setter Property="telerik:StyleManager.Theme" Value="Expression_Dark" />

            <Setter Property="telerik:Theming.Theme" Value="Expression_Dark" />


i can sort the data in RadGridView but the symbol does not change from ascending to

descending.

i need to change the  arrow when clicking on header in RadGridView

is there any way ?

can any one help me .