将XAML TreeViewItem绑定到属性

您好专家.我已经编写了WPF活动库.在其中一个活动中，我使用TreeView在其中显示了一些信息:

Hello experts.I''ve written a WPF activity library.In one of activities I used a TreeView to show some information in it like this :

...
<TreeView x:Name= "myTreeView" Grid.Row="0" FontFamily="Tahoma" FontSize="10">
                    <TreeViewItem Header="Item 1">
                        <TreeViewItem Header="Item 11" >
                            <TreeViewItem Header="Item 111"/>
                            <TreeViewItem Header="Item 112" />
                        </TreeViewItem>
                        <TreeViewItem Header="Item 12" >
                            <TreeViewItem Header="Item 121" />
                            <TreeViewItem Header="Item 122" />
                            <TreeViewItem Header="Item 123" />
                        </TreeViewItem>
                        <TreeViewItem Header="Item 13" >
                            <TreeViewItem Header="Item 131" />
                            <TreeViewItem Header="Item 132" />
                        </TreeViewItem>
                    </TreeViewItem>
                </TreeView>
...

我在Code-Activity端的属性是这样的:

And my property in Code-Activity side is like this :

public InArgument<TreeViewItem> Branch { 
            get{return _branch;} 
            set
            {
                if (this._branch != value)
                {
                    this._branch = value;
                    OnPropertyChanged("Branch");
                }
            } 
        }

        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged(string propertyName)
        {
            if (this.PropertyChanged != null)
            {
                this.PropertyChanged(this, 
                                new PropertyChangedEventArgs(propertyName));
            }
        }

当用户单击TreeView项之一时，我需要将该项发送到我的属性(我想将其绑定到Branch属性).
我该怎么做?

I need when user clicked on one of the TreeView items, I send that item to my property(I want to bind it to Branch property).
How can I do it?