[CE C#] Sizing problem of Toolbar by WPF

When I was trying to play how to use WPF to create a toolbox with VS 2015 Tools for MicroStation CONNECT Edition , I found that I couldn't fix or change the Window size. Glad if someone could provide the comment as following:

1. ResizeMode, WindowStyle cannot help fix the toolbox
2. Toolbar_SizeChanged cannot help resize the toolbox

namespace MSAddinSample
{

    public partial class Toolbox : UserControl
    {
        private static Bentley.MstnPlatformNET.WPF.DockableToolbar currentControl;
        private static Bentley.ResourceManagement.IMatchLifetime BRI;
        private Bentley.MstnPlatformNET.AddIn m_addIn;

        public Toolbox(Bentley.MstnPlatformNET.AddIn addIn)
        {
            m_addIn = addIn;
            InitializeComponent();
            
        }

        internal static void ShowWindow(Bentley.MstnPlatformNET.AddIn addIn)
        {
            if (null != currentControl)
            {
                currentControl.Focus();
                return;
            }
            
            currentControl = new Bentley.MstnPlatformNET.WPF.DockableToolbar();
            currentControl.ResizeMode = System.Windows.ResizeMode.NoResize;
            currentControl.WindowStyle = System.Windows.WindowStyle.ToolWindow;
            currentControl.Content = new Toolbox(addIn);
            currentControl.Attach(BRI, 'control');
            currentControl.Show();
            //currentControl.WindowContent.CanDockVertically = false;
        }

        private void Toolbox_Unloaded(object sender, System.Windows.RoutedEventArgs e)
        {
            currentControl = null;
        }

        private void Toolbar_SizeChanged(object sender, System.Windows.SizeChangedEventArgs e)
        {
            currentControl.Width = 200;
            currentControl.Height = 30;
        }
    }