How can I set default text with GridFilterBehavior?

[zhang]

<telerik:RadWatermarkTextBox x:Name="SearchWatermarkTextBox" Text="{Binding SearchText}"/>
<telerik:RadGridView Name="GridView" behavior:GridFilterBehavior.TextBox="{Binding ElementName=SearchWatermarkTextBox}">

Here is the example code.I can set text in datacontext SearchText property.But when the window opened,I cant see the data without filtered,then the girdview's BusyIndicator has been shown.It looks not good. How to let BusyIndicator be shown when the window opened or let the window opened after data has been filtered?

Thanks

[zhang]

edit:I can see the data without filtered

sorry