Im happy to announce that with our upcoming Q1 2010 Service Pack 1 (middle of April) you will be able to apply conditionally styles and templates for RadGridView easily using DataTemplateSelectors and StyleSelectors for both Silverlight and WPF:

You can test the new functionally with our upcoming latest internal build this Friday and in the meantime here is an example:

XAML

<Grid  x:Name="LayoutRoot">
   <Grid.Resources>
        <local:MyStyleSelector  x:Key="styleSelector" />
        <local:MyDataTemplateSelector  x:Key="templateSelector" />
    </Grid.Resources>
    <telerik:RadGridView  AutoGenerateColumns="False"  ItemsSource="{Binding}"  RowStyleSelector="{StaticResource  styleSelector}">
        <telerik:RadGridView.Columns>
            <telerik:GridViewDataColumn  DataMemberBinding="{Binding  ID}"  CellTemplateSelector="{StaticResource  templateSelector}" />
        </telerik:RadGridView.Columns>
    </telerik:RadGridView>
</Grid>

C#

public class  MyStyleSelector  : StyleSelector
{
  public override  ...

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