Editable grids will quite commonly show an indicator in the row header area to indicate that a row is currently being edited. This is trivial to achieve using Microsoft’s WPF DataGrid.

All that is needed is a DataTemplate assigned to the RowHeaderTemplate property of the DataGrid. The template simply shows or hides the editing image based upon whether the current row is being edited.

<SolidColorBrush x:Key="gridLineBrush" Color="#FFCDEFFE"/>

<DataTemplate x:Key="rowHeaderTemplate">
    <StackPanel Orientation="Horizontal">
        <Image x:Name="editImage" Source="Images/Edit.png" Width="16" Margin="1,0" Visibility="Hidden"/>
    </StackPanel>
    <DataTemplate.Triggers>
        <DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor,
                                       AncestorType={x:Type toolkit:DataGridRow}},Path=Item.IsEditing}" 
                     Value="True">
            <Setter TargetName="editImage" Property="Visibility" Value="Visible"/>
        </DataTrigger>
    </DataTemplate.Triggers>
</DataTemplate>

<Style TargetType="{x:Type toolkit:DataGrid}">
    <Setter Property="GridLinesVisibility" Value="All"/>
    <Setter Property="HorizontalGridLinesBrush" Value="{StaticResource gridLineBrush}"/>
    <Setter Property="VerticalGridLinesBrush" Value="{StaticResource gridLineBrush}"/>
    <Setter Property="RowHeaderTemplate" Value="{StaticResource rowHeaderTemplate}"/>
    <Style.Resources>
        <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="Transparent"/>
        <SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="Black"/>
        <SolidColorBrush x:Key="{x:Static toolkit:DataGrid.FocusBorderBrushKey}" Color="{StaticResource gridLineBrush}"/>
    </Style.Resources>
</Style>

There is an IsEditingRowItem property on the DataGrid but unfortunately its private. As it happens my base model class has an IsEditing property as part of its IEditableObject implementation. So I simply bind the visibility of the image to that.

#region IEditableObject Members

public void BeginEdit()
{
    IsEditing = true;
}

public void CancelEdit()
{
    IsEditing = false;
    // RollbackPropertyValues( _preEditValues );
}

public void EndEdit()
{
    IsEditing = false;
}

#endregion