How to redraw or refresh in OnRender?

Question

I want to draw something dynamically. Following code shows my OnRender. I'm setting DrawItem somewhere in my program where I need it. But when I'm calling DrawItem =5; what do I have to call, so that OnRender gets called?

protected override void OnRender(DrawingContext drawingContext)
{
    switch (DrawItem)
    {
        case 1:
            //Draw Item 
            break;
        case 2:
            //Draw Item 
            break;
        case 3:
            //Draw Item 
            break;
        case 4:
            //Draw Item 
            break;
        case 5:
            //Draw Item 
            break;
    }
    base.OnRender(drawingContext)
}

public int DrawItem { get; set; }

Answer 1

Your question is not clear but from what I can understand you seem to be asking for a method to refresh the visuals after updating your drawing variables. You could use the following after updating your drawing variables:

this.InvalidateVisual();

and with the property:

private int drawItem;
pulic int DrawItem
{
 get {return drawItem;}
 set 
 {
    drawItem=value;
    this.InvalidateVisual();
 }
}