无法为RadDataGrid多选复选框

Question

我可以选中一个复选框，但当我点击另一个复选框时，前一个复选框将被删除。任何帮助将不胜感激。

<telerik:RadGridView Name="Grid" ItemsSource="{Binding Items}"  RowIndicatorVisibility="Collapsed" SelectionMode="Multiple">
    <telerik:RadGridView.Columns>
        <telerik:GridViewCheckBoxColumn DataMemberBinding="{Binding CheckAll}">
             <telerik:GridViewCheckBoxColumn.GroupHeaderTemplate>
         <DataTemplate>
        <CheckBox Checked="CheckAll_Checked" Unchecked="CheckAll_Checked" />
    </DataTemplate>
        </telerik:GridViewCheckBoxColumn.GroupHeaderTemplate>
    </telerik:GridViewCheckBoxColumn>
    <telerik:GridViewDataColumn Header="Date" DataMemberBinding="{Binding Date, StringFormat=d}"/>
    <telerik:GridViewDataColumn Header="Loan Account" DataMemberBinding="{Binding AccountNumber}" />  
     </telerik:RadGridView.Columns>
 </telerik:RadGridView >

检查代码，我希望这是你所指的：

private void CheckAll_Checked(object sender, RoutedEventArgs e)
    {
        Grid.Items.OfType<CashFlowDTO>().ToList().ForEach(x => x.Post = CheckAll);
    }