PaintEventArgs e showing null reference

Question

hi

public void Paint(PaintEventArgs e) //here e is showing null reference in class {"Object reference not set to an instance of an object."}//
{
//Graphics g = e.Graphics;
e.Graphics.DrawRectangle(pen1, rect);
}

how to avoid this I need to draw a rectangle by using class method but when I call paint method showing null reference exception.