C#

<br />
public void OnPaint(object sender,PaintEventArgs e)<br />
{<br />
Graphics g=this.CreateGraphics();<br />
Pen pen=new Pen(Color.Magenta);<br />
Point p1=new Point(index1,index2);<br />
Point p2=new Point(index3,index4);<br />
g.DrawLine(pen,p1,p2);<br />
this.ResetMouseEventArgs();	<br />
}<br />
//Mouse Up and Down Events<br />
public void mouseUp(object sender,MouseEventArgs e)<br />
{<br />
index3=e.X;index4=e.Y;		<br />
this.Paint+=new PaintEventHandler(this.OnPaint);	<br />
Invalidate();<br />
}<br />
public void mouseDown(object sender,MouseEventArgs e)<br />
{<br />
index1=e.X;index2=e.Y;					<br />
}<br />

<br />
                //declaration<br />
		private ArrayList m_arlPoint1 = new ArrayList();<br />
		private ArrayList m_arlPoint2 = new ArrayList();<br />
<br />
		protected override void OnPaint(PaintEventArgs e)<br />
		{<br />
			base.OnPaint(e);<br />
                        //you don't need to creategraphics and attach a handler of Paint event if you'll override this method. (just a tip) :)<br />
<br />
			Pen pen=new Pen(Color.Magenta);<br />
			Point pt1, pt2;<br />
			for (int i = 0; i < m_arlPoint1.Count; i++)<br />
			{<br />
				pt1 = (Point)m_arlPoint1[i];<br />
				pt2 = (Point)m_arlPoint2[i];<br />
				e.Graphics.DrawLine(pen, pt1, pt2);<br />
			}<br />
                        <br />
                        //i think you don't need this one<br />
                        //this.ResetMouseEventArgs(); <br />
		}<br />
<br />
		<br />
		protected override void OnMouseUp(MouseEventArgs e)<br />
		{<br />
			m_arlPoint2.Add(new Point(e.X, e.Y));<br />
			Invalidate();<br />
		}<br />
		protected override void OnMouseDown(MouseEventArgs e)<br />
		{<br />
			m_arlPoint1.Add(new Point(e.X, e.Y));<br />
		}<br />
<br />

int n = textBox1.SelectionStart;
if( textBox1.SelectionLength > 0 )
{
  textBox1.Text = textBox1.Text.Remove( textBox1.SelectionStart, textBox1.SelectionLength );
  if( n > 0 )
  {
    textBox1.SelectionStart = n;
  }
}
else if( textBox1.Text.Length > 0 )
{
  string t = textBox1.Text;
  if( n > 0 )
  {
    textBox1.Text = t.Substring( 0, n - 1 ) + t.Substring( n );
    textBox1.SelectionStart = n - 1;
  }
}