GroupRowStyleSelector

You can use RadGridView's GroupRowStyleSelector property if you need to style group rows differently based on a specific condition.

Bear in mind that the GroupRowStyle takes precedence over the GroupRowStyleSelector and will overwrite it if both are defined simultaneously.

To achieve this, first create a new class that inherits from the StyleSelector class and override its SelectStyle method:

Example 1: The GroupRowStyleSelector class

• C#
• VB.NET

public class GroupRowStyleSelector : StyleSelector 
{ 
    public override Style SelectStyle(object item, DependencyObject container) 
    { 
        var group = item as QueryableCollectionViewGroup; 
        if (group.ItemCount > 1) 
        { 
            return BigGroupStyle; 
        } 
        else 
        { 
            return SmallGroupStyle; 
        } 
    } 
 
    public Style BigGroupStyle { get; set; } 
    public Style SmallGroupStyle { get; set; } 
} 

Public Class GroupRowStyleSelector 
    Inherits StyleSelector 
    Public Overrides Function SelectStyle(item As Object, container As DependencyObject) As Style 
        Dim group = TryCast(item, CollectionViewGroup) 
 
        If group IsNot Nothing Then 
            If group.ItemCount > 1 Then 
                Return BigGroupStyle 
            Else 
                Return SmallGroupStyle 
            End If 
        End If 
 
        Return Nothing 
    End Function 
 
    Public Property BigGroupStyle() As Style 
        Get 
            Return m_BigGroupStyle 
        End Get 
        Set 
            m_BigGroupStyle = Value 
        End Set 
    End Property 
    Private m_BigGroupStyle As Style 
 
    Public Property SmallGroupStyle() As Style 
        Get 
            Return m_SmallGroupStyle 
        End Get 
        Set 
            m_SmallGroupStyle = Value 
        End Set 
    End Property 
    Private m_SmallGroupStyle As Style 
End Class 

In the XAML file, define the style selector as a resource and set the properties of the BigGroupStyle and SmallGroupStyle:

Example 2: Setting the BigGroupStyle and SmallGroupStyle

• XAML

<Window.Resources> 
    <my:GroupRowStyleSelector x:Key="GroupRowStyleSelector"> 
        <my:GroupRowStyleSelector.BigGroupStyle> 
            <Style TargetType="telerik:GroupHeaderRow"> 
                <Setter Property="Background" Value="Red" /> 
            </Style> 
        </my:GroupRowStyleSelector.BigGroupStyle> 
        <my:GroupRowStyleSelector.SmallGroupStyle> 
            <Style TargetType="telerik:GroupHeaderRow"> 
                <Setter Property="Background" Value="Yellow" /> 
            </Style> 
        </my:GroupRowStyleSelector.SmallGroupStyle> 
    </my:GroupRowStyleSelector> 
</Window.Resources> 

If you're using GroupRenderMode="Nested" the style should target the GridViewGroupRow element.

The "my:" prefix before GroupRowStyleSelector specifies the mapping for the namespace of the project: xmlns:my="..."

Finally, set the GroupRowStyleSelector property:

Example 3: Setting the GroupRowStyleSelector property

• XAML

<telerik:RadGridView GroupRowStyleSelector="{StaticResource GroupRowStyleSelector}" /> 

And here is the final result:

Figure 1: The group footer rows styled using the GroupRowStyleSelector property