WPF DataGridTextColumn Tooltip

Question

Is there a way to add tool tip to DataGridColumn header and still retain the sorting functionality. The below code doesnt work(It doesnt display the tooltip)

<toolkit:DataGridTextColumn Header="Test" Width="70" Binding="{Binding TestText}" ToolTipService.ToolTip="{Binding TestText}">

And when I use the code below

<toolkit:DataGridTemplateColumn Header="Test" Width="70">  
              <toolkit:DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding TestText}" ToolTip="{Binding TestText}"  />
                        </DataTemplate>
                    </toolkit:DataGridTemplateColumn.CellTemplate>
                </toolkit:DataGridTemplateColumn>

The column loses sorting functionality..Help!

Answer 1

To get the ToolTip to display in the DataGridColumnHeader you'll need to bind the ToolTip property for it to the ToolTip of its DataGridColumn like this

<toolkit:DataGridTextColumn Header="Test"
                            Width="70"
                            Binding="{Binding TestText}"
                            ToolTipService.ToolTip="My Tooltip Text">
    <toolkit:DataGridTextColumn.HeaderStyle>
        <Style TargetType="toolkit:DataGridColumnHeader">
            <Setter Property="ToolTip"
                    Value="{Binding RelativeSource={RelativeSource Self},
                                    Path=Column.(ToolTipService.ToolTip)}"/>
        </Style>
    </toolkit:DataGridTextColumn.HeaderStyle>
</toolkit:DataGridTextColumn>

Answer 2

When the grid creates automatic columns, it knows which field is being displayed in that column. When you create the column yourself, the data grid doesn't know what data you'll be displaying in that column and so it cannot guess which field to sort the column by. To make a column you define yourself sortable, add the SortMemberPath property to your DataGridTemplateColumn like this:

<DataGridTemplateColumn Header="Test" Width="70" SortMemberPath="TestText">
    ...
</DataGridTemplateColumn>