正则表达式不匹配

Question

How can I write a RegEx expression to match the number begin with 090 or 091 or 0123 or 0168 or 0199 or 0124 and the length between 10 to 11 digits?

I try this but not true

@"^(090|091|0123|0168|0199|0124)\d{7,8}$"

Answer 1

The regex itself looks mostly OK, although of course it will allow 12-digit numbers, too (a four-digit start, followed by 8 further digits). To change that, I propose this:

foundMatch = Regex.IsMatch(subjectString, 
    @"^                       # Start of string
    (?=.{10,11}$)             # Assert 10-11 character length
    0                         # Start with matching a 0
    (?:90|91|123|168|199|124) # then one of the alternatives
    [0-9]*                    # then fill the rest with digits.
    $                         # End of string", 
    RegexOptions.IgnorePatternWhitespace);

If you want to find numbers like that in a longer string, not validate a string, then use

resultString = Regex.Match(subjectString, 
    @"\b                      # Start of number
    (?=[0-9]{10,11}\b)        # Assert 10-11 character length
    0                         # Match 0
    (?:90|91|123|168|199|124) # then one of the alternatives
    [0-9]*                    # then fill the rest with digits
    \b                        # End of number", 
    RegexOptions.IgnorePatternWhitespace).Value;

(assuming that the numbers are surrounded by non-alphanumeric characters).