public void AddLineNumbers()
{
// create & set Point pt to (0,0)
Point pt = new Point(0, 0);
// get First Index & First Line from richTextBox1
int First_Index = TxtEditorTexto.GetCharIndexFromPosition(pt);
int First_Line = TxtEditorTexto.GetLineFromCharIndex(First_Index);
// set X & Y coordinates of Point pt to ClientRectangle Width & Height respectively
pt.X = ClientRectangle.Width;
pt.Y = ClientRectangle.Height;
// get Last Index & Last Line from richTextBox1
int Last_Index = TxtEditorTexto.GetCharIndexFromPosition(pt);
int Last_Line = TxtEditorTexto.GetLineFromCharIndex(Last_Index);
// set Center alignment to LineNumberTextBox
LineNumberTextBox.SelectionAlignment = HorizontalAlignment.Center;
// set LineNumberTextBox text to null & width to getWidth() function value
LineNumberTextBox.Text = "";
LineNumberTextBox.Width = getWidth();
// now add each line number to LineNumberTextBox upto last line
for (int i = First_Line; i <= Last_Line; i++)
{
LineNumberTextBox.Text += i + 1 + "\n";
}
}
