dt3 = New System.Data.DataTable("Cat")
        dap3 = New SqlDataAdapter(sql, strConnSQLServer)
        dt3.Columns.Add("id")
        dt3.Columns.Add("Main")
        dt3.Columns.Add("IsDefault") ' checkbox
        dap3.Fill(dt3)
        GridMain.ItemsSource = dt3.DefaultView

<DataGrid x:Name="GridMain" AutoGenerateColumns="False"  HorizontalAlignment="Left" Height="90" Margin="380,460,0,0" VerticalAlignment="Top" Width="408">
            <DataGrid.Columns>
                <DataGridTextColumn Binding="{Binding id}" Header="id"/>
                <DataGridTextColumn Binding="{Binding Main}" Header="Main"/>
                <DataGridTemplateColumn Header="IsDefault">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <CheckBox x:Name="IsDefault" IsChecked="{Binding IsDefault}"    />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>

            </DataGrid.Columns>
        </DataGrid>