Handling backspace in a scrolling RichTextBox

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Hello,

I have a scrolling RichTextBox to which I add characters one at a time using
the AppendText method as they are received by my application. Some of these
characters may be backspace characters, which I need to somehow use to erase
the most recent character displayed in the last line displayed in the text
box. Of course, the backspace must only apply to the last line and must not
back up into the previous line once all characters are removed from the last
line. I would appreciate any suggestions, code references, etc. that anyone
can provide regarding this issue.

Another related issue: I understand that each line in the tesx box is
represented by an array of strings, which continues increasing in size as new
lines are appended. Ultimately I would like to stop this increase by
removing the first string in the array as each new line is appended. I
assume this is done by somehow deleting the first element of the string array
then repainting the text box. Again, I'm pretty vague on the details of
doing this so any suggestions are welcomed.

Thanks,
Ray