wpf 在模板里命令绑定失效

<TreeView x:Name="treeView" Margin="0,0,20,28" Grid.RowSpan="2" >
                <HierarchicalDataTemplate ItemsSource="{Binding xx}" >
                    <TextBlock  Name="tbk" Text="{Binding 部门}" Padding="2"  >
                         <i:Interaction.Triggers >
                              <i:EventTrigger EventName="MouseRightButtonDown">
                                <i:InvokeCommandAction Command="{Binding Path=TbkComm}"  CommandParameter="{Binding ElementName=tbk}"/>
                            </i:EventTrigger> 
                         </i:Interaction.Triggers>
                    </TextBlock>
                    <HierarchicalDataTemplate.ItemTemplate>
                        <DataTemplate>
                            <TextBlock Name="tbk" Text="{Binding 部门}" >
                            </TextBlock>
                        </DataTemplate>
                    </HierarchicalDataTemplate.ItemTemplate>
                </HierarchicalDataTemplate>
            </TreeView.ItemTemplate>

        </TreeView>

                后台
                private static UICommand tbkComm;
        public static UICommand TbkComm
        {
            get { return txtBoxComm; }
            set { txtBoxComm = value; }
        }
        public void getDateSet()//这个是构造器
        {

           TxtBoxComm .ExecuteAction = new Action<object>(事件);

        }