Binding XAML TreeViewItem to a property

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C#

XAML

WPF

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>
...

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));
            }
        }

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?