title: Unintentional space in DataGrid Header columns in C#
body: <p>I have unmeant space in my DataGrid between the last Header column and the Header column before last. The background color of the space is like the App background color (#FF454545). The background colors of my Header columns are individually set. Did I ignore something that evokes this issue?</p>
  
  <p>Here is my code:</p>
  
  <pre><code>&lt;DataGrid Name="dgUserFiles" ItemsSource="{Binding UserFilesObject}" AutoGenerateColumns="False" CanUserAddRows="false"&gt;
      &lt;DataGrid.RowStyle&gt;
          &lt;Style TargetType="DataGridRow"&gt;
              &lt;Style.Triggers&gt;
                  &lt;Trigger Property="IsMouseOver" Value="True"&gt;
                      &lt;Setter Property="Background" Value="#FF454545" /&gt;
                  &lt;/Trigger&gt;
              &lt;/Style.Triggers&gt;
          &lt;/Style&gt;
      &lt;/DataGrid.RowStyle&gt;
      &lt;DataGrid.Columns&gt;
          &lt;DataGridTextColumn Header="File" Width="3*" Binding="{Binding File}" IsReadOnly="True"&gt;
              &lt;DataGridTextColumn.HeaderStyle&gt;
                  &lt;Style TargetType="DataGridColumnHeader"&gt;
                      &lt;Setter Property="Background" Value="#FF454545" /&gt;
                      &lt;Setter Property="HorizontalContentAlignment" Value="Left"/&gt;
                  &lt;/Style&gt;
              &lt;/DataGridTextColumn.HeaderStyle&gt;
          &lt;/DataGridTextColumn&gt;
          &lt;DataGridTextColumn Header="Last Check" Width="2*" Binding="{Binding LastCheck}" IsReadOnly="True"&gt;
              &lt;DataGridTextColumn.HeaderStyle&gt;
                  &lt;Style TargetType="DataGridColumnHeader"&gt;
                      &lt;Setter Property="Background" Value="#FF454545" /&gt;
                      &lt;Setter Property="HorizontalContentAlignment" Value="Left"/&gt;
                  &lt;/Style&gt;
              &lt;/DataGridTextColumn.HeaderStyle&gt;
          &lt;/DataGridTextColumn&gt;
          &lt;DataGridTextColumn Header="Next Check" Width="2*" Binding="{Binding NextCheck}" IsReadOnly="True"&gt;
              &lt;DataGridTextColumn.HeaderStyle&gt;
                  &lt;Style TargetType="DataGridColumnHeader"&gt;
                      &lt;Setter Property="Background" Value="#FF454545" /&gt;
                      &lt;Setter Property="HorizontalContentAlignment" Value="Left"/&gt;
                  &lt;/Style&gt;
              &lt;/DataGridTextColumn.HeaderStyle&gt;
          &lt;/DataGridTextColumn&gt;
          &lt;DataGridTextColumn Header="Status" Width="1*" Binding="{Binding Status}" IsReadOnly="True"&gt;
              &lt;DataGridTextColumn.HeaderStyle&gt;
                  &lt;Style TargetType="DataGridColumnHeader"&gt;
                      &lt;Setter Property="Background" Value="#FF454545" /&gt;
                      &lt;Setter Property="HorizontalContentAlignment" Value="Left"/&gt;
                  &lt;/Style&gt;
              &lt;/DataGridTextColumn.HeaderStyle&gt;
              &lt;DataGridTextColumn.ElementStyle&gt;
                  &lt;Style TargetType="{x:Type TextBlock}"&gt;
                      &lt;Style.Triggers&gt;
                          &lt;Trigger Property="Text" Value="Readable"&gt;
                              &lt;Setter Property="Foreground" Value="Green"/&gt;
                          &lt;/Trigger&gt;
                          &lt;Trigger Property="Text" Value="Not Readable"&gt;
                              &lt;Setter Property="Foreground" Value="Red"/&gt;
                          &lt;/Trigger&gt;
                      &lt;/Style.Triggers&gt;
                  &lt;/Style&gt;
              &lt;/DataGridTextColumn.ElementStyle&gt;
          &lt;/DataGridTextColumn&gt;
          &lt;DataGridTemplateColumn Header="Action" Width="1*"&gt;
              &lt;DataGridTemplateColumn.HeaderStyle&gt;
                  &lt;Style TargetType="DataGridColumnHeader"&gt;
                      &lt;Setter Property="Background" Value="#FF454545" /&gt;
                      &lt;Setter Property="HorizontalContentAlignment" Value="Center"/&gt;
                  &lt;/Style&gt;
              &lt;/DataGridTemplateColumn.HeaderStyle&gt;
              &lt;DataGridTemplateColumn.CellTemplate&gt;
                  &lt;DataTemplate&gt;
                      &lt;StackPanel Orientation="Horizontal" HorizontalAlignment="Center"&gt;
                          &lt;Button Click="btnDgUserFiles_CheckNow_Click"&gt;
                              &lt;StackPanel Orientation="Horizontal"&gt;
                                  &lt;Rectangle Width="12" Height="12" Fill="{Binding RelativeSource={RelativeSource AncestorType=Button}, Path=Foreground}"&gt;
                                      &lt;Rectangle.OpacityMask&gt;
                                          &lt;VisualBrush Stretch="Fill" Visual="{StaticResource appbar_refresh}" /&gt;
                                      &lt;/Rectangle.OpacityMask&gt;
                                  &lt;/Rectangle&gt;
                              &lt;/StackPanel&gt;
                          &lt;/Button&gt;
                          &lt;Button Click="btnDgUserFiles_Delete_Click"&gt;
                              &lt;StackPanel Orientation="Horizontal"&gt;
                                  &lt;Rectangle Width="12" Height="12" Fill="{Binding RelativeSource={RelativeSource AncestorType=Button}, Path=Foreground}"&gt;
                                      &lt;Rectangle.OpacityMask&gt;
                                          &lt;VisualBrush Stretch="Fill" Visual="{StaticResource appbar_delete}" /&gt;
                                      &lt;/Rectangle.OpacityMask&gt;
                                  &lt;/Rectangle&gt;
                              &lt;/StackPanel&gt;
                          &lt;/Button&gt;
                      &lt;/StackPanel&gt;
                  &lt;/DataTemplate&gt;
              &lt;/DataGridTemplateColumn.CellTemplate&gt;
          &lt;/DataGridTemplateColumn&gt;
      &lt;/DataGrid.Columns&gt;
  &lt;/DataGrid&gt;
  </code></pre>
  
  <p>This is the screenshot:
  <img src="https://i.stack.imgur.com/peuil.png" alt="enter image description here"></p>