# V3122. Uppercase (lowercase) string is compared with a different lowercase (uppercase) string.

The analyzer detected a comparison of two strings whose characters are in different cases.

Consider the following example:

    void Some(string s)
    {
      if (s.ToUpper() == "abcde")
      {
        ....
      }
    }

After casting the 's' variable's value to upper case, the resulting string is compared with a string where all the characters are lowercase. As this comparison is always false, this code is incorrect and can be fixed in the following way:

    void Some(string s)
    {
      if (s.ToLower() == "abcde")
      {
        ....
      }
    }

Consider another example:

    void Some()
    {
      string s = "abcde";
      ....
      if (s.Contains("AbCdE"))
      {
        ....
      }
    }

While all the characters of the 's' variable's value are lowercase, an attempt is made to check if the string contains a mixed-case substring. Obviously, the 'Contains' method will always return 'false', which also indicates an error.

This diagnostic is classified as:

CWE-570

You can look at examples of errors detected by the V3122 diagnostic.