Bind width on UI element to Width of another UI Element

I wanted to bind Width of a column header to the Width of the header defined. However the code doesn't work. If I specify the Width explicitly (Width="100"), it works fine. Can someone shed some light and tell me what is wrong with the code below?

<dataGrid:DataGridTemplateColumn x:Name="pdpCol" Width="100">
        <dataGrid:DataGridTemplateColumn.Header>
           开发者_运维知识库 <Grid HorizontalAlignment="Stretch">
                <TextBlock Text="PDP" VerticalAlignment="Center" HorizontalAlignment="Center" 
                    TextWrapping="Wrap" Width="{Binding ElementName=pdpCol,Path=ActualWidth }" TextAlignment="Center" />
            </Grid>
        </dataGrid:DataGridTemplateColumn.Header>
</dataGrid:DataGridTemplateColumn>

Remove the HorizontalAlignment="Center" from the TextBlock or set the property to Stretch. Then the TextBlock will consume all available width automatically. Furthermore, if you don't show anything else than the textblock, then remove the grid and use just the TextBlock. You also need to set HeaderTemplate rather the Header directly.

<dataGrid:DataGridTemplateColumn x:Name="pdpCol" Width="100" Header="PDP">
    <dataGrid:DataGridTemplateColumn.HeaderTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding}" TextAlign="Center" />
        </DataTemplate>
    </dataGrid:DataGridTemplateColumn.HeaderTemplate>
</dataGrid:DataGridTemplateColumn>

Best Regards,
Oliver Hanappi

Try the markup below. Please note the use of HeaderStyle to stretch the template and HeaderTemplate to actually define the visual template for your Header="PDP" item.

<dataGrid:DataGridTemplateColumn x:Name="pdpCol" Width="100" Header="PDP">
    <dataGrid:DataGridTemplateColumn.HeaderStyle>
         <Style TargetType="{x:Type Primitives:DataGridColumnHeader}">
              <Setter Property="HorizontalContentAlignment" Value="Stretch" />
              <Setter Property="VerticalContentAlignment" Value="Center" />
         </Style>
    </dataGrid:DataGridTemplateColumn.HeaderStyle>
    <dataGrid:DataGridTemplateColumn.HeaderTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding}" TextAlignment="Center" />
        </DataTemplate>
    </dataGrid:DataGridTemplateColumn.HeaderTemplate>
</dataGrid:DataGridTemplateColumn>

Check if ActualWidth is being set, I think it will work if you just use Path=Width.