VB.NET From 'A' to 'ZZZ' : I have seen this in c# and I'm using VB.net. This code is related somehow to what output I want to be

    string increment(string str) {        
      char[] digits = str.ToCharArray();
    
      for (int i = str.length - 1; i >= 0; --i) {
        if (digits[i] == 'Z') {
          digits[i] = 'A';
        } else {
          digits[i] += 1;
          break;
        }
      }
      return new string(digits);
    }

I want to increment 'A' to 'ZZZ' just like from 0 to 999. Where the sequence is like this

    AAA 
    AAB 
    AAC 
    ... 
    AAZ

And after the 'AAZ' it will proceed to

    ABA
    ABC
    ABD
    ABE
    ...
    ABZ

And so on and so fort up to 'ZZZ'

And also detects lower case or upper case

Thanks in advance for help