this.CreateGraphics().DrawLine(new Pen(Color.Red, 10), 10, 10, 100, 100);

ArrayList lines = new ArrayList();

private void addButton_Click(object sender, System.EventArgs e)
{		
	Line line = new Line();
	line.StartPoint = new Point(10, 10);
	line.EndPoint = new Point(100,100);
	line.Color = Color.Red;
	line.Width = 10;

	lines.Add(line);

	//Переисовка
	//this.Invalidate(); //Весь экран
	this.Invalidate(new Rectangle(0, 0, 110, 110));//Если только часть экрана
}

private void removeButton_Click(object sender, System.EventArgs e)
{
	if (lines.Count > 0)
	{
		//Удаляем из коллекции
		lines.RemoveAt(0);
	}			
	this.Invalidate(new Rectangle(0, 0, 110, 110));//Если только часть экрана
}

protected override void OnPaint(PaintEventArgs e)
{
	foreach (Line line in lines)
	{
		e.Graphics.DrawLine(new Pen(line.Color, line.Width), line.StartPoint, line.EndPoint);		
	}
	base.OnPaint (e);
}	

internal struct Line
{
	public Point StartPoint;
	public Point EndPoint;
	public Color Color;
	public int Width;
}