Custom Control ControlTemplate 一些控件不能双向绑定
<telerik:RadMaskedTextBox Grid.Column="0" Grid.ColumnSpan="2" x:Name="PART_txtSearch" MinHeight="0" MinWidth="0" MaskType="None" SelectionOnFocus="SelectAll" Value="{Binding SearchStr,RelativeSource={RelativeSource TemplatedParent},Mode=TwoWay}" EmptyContent="{TemplateBinding EmptyString}" />