api.cs

// create a new donut shape
TXTextControl.Drawing.Shape shape =
    new TXTextControl.Drawing.Shape(TXTextControl.Drawing.ShapeType.Donut);

// set the color and border width
shape.ShapeFill.Color = Color.Red;
shape.ShapeOutline.Color = Color.Yellow;
shape.ShapeOutline.Width = 200;

if (textControl1.Drawings.GetActivatedItem() != null)
{
    // add the shape to the drawing control
    ((TXDrawingControl)textControl1.Drawings.GetActivatedItem().Drawing).Shapes.Add(shape);
}