向大家请教一个 wpf 绑定值得问题

Question

xaml:

<UserControl.Resources>    
<ResourceDictionary>
   <DataTemplate x:Key="DateTemplate" >
                <DatePicker Name="EditDateTime" SelectedDate="{Binding OpValue}"></DatePicker>
            </DataTemplate>
            <DataTemplate x:Key="TxtTemplate">
                <TextBox Name="EditTxt" Text="{Binding OpValue}"></TextBox>
            </DataTemplate>
        </ResourceDictionary>        
    </UserControl.Resources>
 
<DataGrid Margin="5" Grid.Row="1" CanUserAddRows="False" Name="DGList2" >
                <DataGrid.Columns>
                <DataGridComboBoxColumn Header="逻辑关系" Width="100"  ItemsSource="{x:Static local:aSearch.opLogic}" DisplayMemberPath="SName"  SelectedValuePath="SValue" TextBinding="{Binding Path=OpLogic}" ></DataGridComboBoxColumn>
                <DataGridComboBoxColumn Header="查询字段" Width="100" ItemsSource="{x:Static local:aSearch.opFields}" DisplayMemberPath="SName"  SelectedValuePath="SValue" TextBinding="{Binding Path=OpField}"></DataGridComboBoxColumn>
<DataGridComboBoxColumn Header="比较符" Width="100" ItemsSource="{x:Static local:aSearch.opMark}" DisplayMemberPath="SName"  SelectedValuePath="SValue" TextBinding="{Binding Path=OpMark}"></DataGridComboBoxColumn>                
                <DataGridTemplateColumn Header="查询值" Width="100"
                        >                    
                </DataGridTemplateColumn>
                 
            </DataGrid.Columns>
 
            </DataGrid>

后台代码如下：

ObservableCollection<Model.SearchList> source = new ObservableCollection<Model.SearchList>();
 
public static List<SearchModel> opLogic = new List<SearchModel>() { 
        new SearchModel() {  SName="并且",SValue="and"},
        new SearchModel() {  SName="或者",SValue="or"}
        };
        public static List<SearchModel> opMark = new List<SearchModel>() { 
        new SearchModel() {  SName="等于",SValue="=",DataType="number,string,date"},
        new SearchModel() {  SName="大于",SValue=">",DataType="number,date"},
        new SearchModel() {  SName="大于等于",SValue=">=",DataType="number,date"},
        new SearchModel() {  SName="小于",SValue="<"},
        new SearchModel() {  SName="小于等于",SValue="<="},
        new SearchModel() {  SName="包含",SValue="like"},
        new SearchModel() {  SName="不包括",SValue="not like"}
        };
        public static List<SearchModel> opFields = new List<SearchModel>() { 
        new SearchModel() {  SName="字符串类型",SValue="FBillNo",DataType="string"},
        new SearchModel() {  SName="日期类型",SValue="FDate",DataType="date"}
        };
 
public aSearch()
        {
            InitializeComponent();
            DGList2.ItemsSource = source;            
        }
 
private void DGList2_CellEditEnding(object sender, DataGridCellEditEndingEventArgs e)
        {                        
            var curItem = e.Row.Item as Model.SearchList;
            switch (e.Column.Header.ToString())
            {
                case "查询字段":
                    var fieldValue = (e.EditingElement as ComboBox).SelectedValue.ToString();
                    if (fieldValue != curItem.OpField) {
                        DataGridCell cell = DGList2.GetCell(DGList2.Items.IndexOf(e.Row.Item), DGList2.Columns.IndexOf(e.Column) + 2);
                        if (fieldValue.Equals("FDate"))
                        {
                            cell.ContentTemplate = this.FindResource("EditingDateTemplate") as DataTemplate; 
                        }
                        else
                            cell.ContentTemplate = this.FindResource("EditingDateTemplate2") as DataTemplate;
                    }
                    break;
            }
 
 
        }

现在主要问题是：查询值里面的内容没有绑定到 source 集合里面对应对象的 OpValue属性中。

我输出的都是空的内容。。
输出代码如下：  

MessageShow(source.First().OpValue);

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^_^