Add lines on each canvas invalidation from a list of lines in WPF

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WPF

C#6.0

I have a code for drawing line on a canvas in wpf. The line is drawn using a mouse event. When the line is drawn it is also added to a list of Lines. I want to redraw those lines each time the canvas invalidate like we do in Paint event of winform Panel.

private void Panel_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    line = true;
    Point pointToWindow = Mouse.GetPosition(this);
    Point pointToScreen = PointToScreen(pointToWindow);
    DsP1 = new Point(pointToWindow.X, pointToWindow.Y - 150);
    if (e.ButtonState == MouseButtonState.Released)
    {
        line = false;
        ln = new System.Windows.Shapes.Line();
        ln.X1 = DsP1.X;
        ln.Y1 = DsP1.Y;
        ln.X2 = e.GetPosition(Panel).X;
        ln.Y2 = e.GetPosition(Panel).Y;
        ln.Stroke = pen;
        Panel.Children.Add(ln);
        Lines.Add(ln);
    }
}

private void Panel_MouseMove(object sender, MouseEventArgs e)
{

    if (line == true && e.LeftButton==MouseButtonState.Pressed)
    {
        Panel.Children.Remove(ln);
        ln = new System.Windows.Shapes.Line();
        ln.X1 = DsP1.X;
        ln.Y1 = DsP1.Y;
        ln.X2 = e.GetPosition(Panel).X;
        ln.Y2 = e.GetPosition(Panel).Y;
        ln.Stroke = pen;
        Panel.Children.Add(ln);
    }

}

What I have tried:

I have tried overriding render with..

protected override void OnRender(DrawingContext drawingContext)
        {
            base.OnRender(drawingContext);
            foreach(Line l in Lines){
Panel.Childeren.add(l);
}
           
        }

it doesn't work... any idea