Load multiple text file in simple Notepad

Question

How we load multiple text file in our simple notepad application?
We can build a simple notepad just using rich text box or text box and open, save dialog. but in single time we only open a single file. If i open "a.txt" then when i try to open "b.txt" first file will gone.

I want to try both file will be there with separate tab.(like Notepad++).

How i do that?

First i think the rich text box will be in different form & when open any file or create new file that form will appear. But I am not implement it as it not looks like Notepad++.

if we use Tab control then i think, the close button will not appear in tab.

Please help me!

Thank you in advance!