String.replace adding extra characters - vb.net

Question

I am trying to replace some words in mails in Outlook. Here is my code for it
Dim input As String = mail.HTMLBody
Dim pattern As String = "QWQ[a-z][a-z][0-9][0-9][0-9][0-9][0-9]"
Dim replacement As String
Dim rgx As New Regex(pattern)
Dim match As Match = Regex.Match(input, pattern)
While (match.Success)
replacement = "A" + match.Value + "A"
input = input.Replace(match.value, replacement)
match = match.NextMatch()
End While
mail.HTMLBody = input
For this input
QWQrt12345
QWQrt1234533
wwQWQrt12345
QWQrt1234534
qwwQWQrt12345
I expect output as
AQWQrt12345A
AQWQrt12345A33
wwAQWQrt12345A
AQWQrt12345A34
qwwAQWQrt12345A
But the output I am getting is
AAAAAQWQrt12345AAAAA
AAAAAQWQrt12345AAAAA33
wwAAAAAQWQrt12345AAAAA
AAAAAQWQrt12345AAAAA34
qwwAAAAAQWQrt12345AAAAA
What can be the issue?

Answer 1

The description of String.Replace states,
Returns a new string in which all occurrences of a specified string in
the current instance are replaced with another specified string.
The important takeaway there is, "all occurrences ... are replaced." Since your replacement string is also a match for your regular expression pattern, it will be replaced (thus adding another set of 'A') upon every iteration.
Try a test case using something like this, instead:
replacement = match.Value.Replace("Q", "A")
The details here don't matter (you can change whatever you want), the point is that you change something so that your strings aren't matched repeatedly.

Answer 2

simply put your adding 'A' + match + 'A' evertytime you match .
Resulting in the AAAAA before and after your input. I've been voted down?
ok I explain your first match input result is exactly what you have inputted(all characters could be matched), you then add "A" both sides and want to replace your replaced value with the original value.
Here's the c# code to get expected value :
var input = "QWQrt1234533"; //your second line example
const string pattern = "QWQ[a-z][a-z][0-9][0-9][0-9][0-9][0-9]";
var rgx = new Regex(pattern);
Match match = Regex.Match(input, pattern);
while (match.Success)
{
var replacement= "A" + match.Value + "A";
input = input.Replace(match.Value, replacement);
match = match.NextMatch();
}
Console.Write(input);
resulting in your exected : "AQWQrt12345A33"
not getting your results even with the posted VB code (you did not edit the original after my first response?)