a notepad with line numbering enhancement

Question

hi every body , i want to make a notepad with the ability to add line numbers to every line(like the visual studio editor), the numbers must be ignored when saving the file, ihave made a text box for the file text and another to show the line numbers, when ever a new line is read a new number will appear in the line number text box, i need to know how to modify the line numbers whenever the file text box is resized changed. regards...