Code

private void Form1_Load(object sender, System.EventArgs e)
{
	fc.ModificationStart = ModificationStyle.SelectedOnly;
	fc.Selection.AllowMultiSel = false;
	fc.CustomBehavior = new ReadOnlyBehavior(fc);
}

class ReadOnlyBehavior : ModifyBehavior
{
	public ReadOnlyBehavior(FlowChart flowChart) : base(flowChart)
	{
	}

	public override InteractionState StartDraw(PointF point)
	{
		return new InteractionState(FlowChart.Selection, -1, Action.Create);
	}

	public override bool SetMouseCursor(PointF point)
	{
		return false;
	}
}