Simple Numeric Edit Control

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In our application we needed several edit controls to accept only numbers.
One might think to use the Number option on the resource editor, but
unfortunately that did not allow us to enter the “-” minus sign. So we
needed a different solution.

We looked at CodeGuru to find a simple MaskEdit control. There were several
to choose from but unfortunately they all did much more that we needed, and
the cursor movement, backspace and delete were not exactly the same as the
standard edit control (which was a requirement). With nothing else to do,
we (like so many others other there) simply wrote our own.

It was unbelievably simple. Here are the steps we took:

1: Created a new class using class wizard where the base class was CEdit.
2: Added this handler for WM_CHAR

void MaskEdit::OnChar(UINT nChar, UINT nRepCnt, UINT nFlags)
{
 CString Holder =
  "`[email protected]#$%^&*()_+|=\\qwertyuiop[]asdfghjkl;'zxcvbnm,./QWERTYUIOP{}ASDFGHJKL:/\"
  "ZXCVBNM<>/";

 if(Holder.Find(nChar)!=-1)
  return;

 CEdit::OnChar(nChar, nRepCnt, nFlags);
}

That’s it. No it does not check for every possibility in the world, but it
does exactly what we needed. It allows us to have an edit control that
works exactly like the default, but only allows numbers and the “-” sign.
There is probably a more elegant way we could have done this, but this was
fast, and it worked.

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