Change the background color of a single DataGrid column header

Question

I'm using a WPF DataGrid and I want to change a single column header background color, without affecting the others.

I found the following question:

How to change column header's background color when using WPF datagrid,

but this will change all column headers, and I only want to change one.

Answer 1

When you use something like that:

<DataGrid>
  <DataGrid.Resources>
    <Style TargetType="{x:Type DataGridColumnHeader}">
      <Setter Property="Background" Value="Blue" />
    </Style>
  </DataGrid.Resources>
</DataGrid>

you're changing the DataGridColumnHeader Style for ALL the ColumnHeaders in that scope, because the Style has not been given a Key.

Now, pretend that the ItemsSource of the DataGrid is a List<C>, where C is a class with string properties called A and B. This is what you can do to set only the Style of column A:

<DataGrid>
  <DataGrid.Resources>
    <Style TargetType="{x:Type DataGridColumnHeader}"
           Key="SpecialHeaderStyle"> <!-- here I set the Style's Key -->
      <Setter Property="Background" Value="Blue" />
    </Style>
  </DataGrid.Resources>
  <DataGrid.Columns>
    <!-- for this column I set the HeaderStyle property -->
    <DataGridTextColumn Binding="{Binding A}"
                        Header="A"
                        HeaderStyle="{StaticResource SpecialHeaderStyle}"/>
    <!-- for this column I don't -->
    <DataGridTextColumn Binding="{Binding B}"
                        Header="B"/>
  </DataGrid.Columns>
</DataGrid>

You'll the special Style set only on Column A.

Just as an aside, give attention to this: if you change the Style in this way, you're setting a fixed background color that is not changing if you pass over with the Mouse. In order to make a more responsive header UI, you have to override its whole Template. Read this for a wider discussion.