无法在datagrid中刷新WPF Combobox

Question

我是WPF的新手，我需要根据datagrid外部的按钮单击将dataobrid绑定到datagrid中。每次当我点击数据网格内的按钮组合框时都应该刷新。

我能够绑定源列组合框但是当我通过更改源文件单击“应用”按钮时它没有刷新，如上图所示。

我为此做的XAML代码是

<Grid Name="grdMappedTables" Margin="0,109,466,28" Background="LightGray">
<Grid.Resources>
                      <ObjectDataProvider x:Key="SourceDataProvider" ObjectType="{x:Type local:SourceTable}" MethodName="FillSourceTableCol" ></ObjectDataProvider>

  </Grid.Resources>
<DataGrid Name="dgMappedTables" RenderOptions.ClearTypeHint="Enabled" TextOptions.TextFormattingMode="Display" CanUserAddRows="False"
                                SelectionUnit="FullRow" Style="{DynamicResource AzureDataGrid}" GridLinesVisibility="All" AutoGenerateColumns="False" BorderBrush="Black" BorderThickness="1">
         <DataGrid.Columns>
               <DataGridTextColumn  Width="25" IsReadOnly="True" CanUserResize="False"  >
               </DataGridTextColumn>

               <DataGridComboBoxColumn Header="Source" Width="200" CanUserResize="False" SelectedValueBinding="{Binding Path=column_id}" SelectedValuePath="column_id" DisplayMemberPath="column_name" ItemsSource="{Binding Source={StaticResource SourceDataProvider}}">
                                 <DataGridComboBoxColumn.EditingElementStyle>
                            <Style TargetType="ComboBox">
                                   <Setter Property="IsEditable" Value="False"></Setter>
                             </Style>
                                    </DataGridComboBoxColumn.EditingElementStyle>
                                </DataGridComboBoxColumn>

                                <DataGridComboBoxColumn Header="Target" Width="200" CanUserResize="False" >

                                </DataGridComboBoxColumn>                                 
                            </DataGrid.Columns>
 </DataGrid>
 </Grid>

类后面的代码用于此

public class SourceTable
{
    public DataView FillSourceTableCol()
    {
        DataTable dtSourceTable = new DataTable();
        dtSourceTable = CommonDBClass.GetTable("select column_id, column_name from systabcol", strConnectionString);
        return dtSourceTable.DefaultView;
    }
}

单击“应用”按钮时，如何刷新组合框？