I keep getting this button in the header, I can click on the button to select all rows. This misaligns the data from the header. Any ideas? Thanks in Advance.

<dg:DataGrid.Columns>

    <dg:DataGridTextColumn Header="Description" Width=".5*"

                           Binding="{Binding Description}">

    </dg:DataGridTextColumn>

    <dg:DataGridTextColumn Header="Type" Width="100" Binding="{Binding Type}">

    </dg:DataGridTextColumn>

    <dg:DataGridTextColumn Header="Amount $" Width="100" Binding="{Binding Amount}">

    </dg:DataGridTextColumn>

    <dg:DataGridTextColumn Header="Effective From Date" Width="100" Binding="{Binding EffectiveFromDate}"

                           IsReadOnly="True">

    </dg:DataGridTextColumn>

    <dg:DataGridTextColumn Header="Effective To Date" Width="100" Binding="{Binding EffectiveToDate}"

                           IsReadOnly="True">

    </dg:DataGridTextColumn>

    <dg:DataGridTextColumn Header="Status" Width="100" Binding="{Binding Status}">

    </dg:DataGridTextColumn>

</dg:DataGrid.Columns>