Data binding to SelectedItem in a WPF Treeview

Question

How can I retrieve the item that is selected in a WPF-treeview? I want to do this in XAML, because I want to bind it.

You might think that it is SelectedItem

Answer 1

After studying the Internet for a day I found my own solution for selecting an item after create a normal treeview in a normal WPF/C# environment

private void BuildSortTree(int sel)
        {
            MergeSort.Items.Clear();
            TreeViewItem itTemp = new TreeViewItem();
            itTemp.Header = SortList[0];
            MergeSort.Items.Add(itTemp);
            TreeViewItem prev;
            itTemp.IsExpanded = true;
            if (0 == sel) itTemp.IsSelected= true;
            prev = itTemp;
            for(int i = 1; i