正则表达式，用于使用CSV将字符串格式验证为特定长度

Question

I am trying to write a regular expression which validates a text box to have only digits with length 5 or 9. I found the below regular expression to get this done

^\d{1,5}([,]\d{5})*$

but it could not fix my requirement correctly, Can any one please help me in modifying or writing a new regular expression which supports below pattern.

• 09103,09101, valid (ending with comma)
• 09103,09101 valid (not ending with comma)
• 12345,1234567 Invalid (should not support if 1st digit is length 5 and 2nd less than 9)
• 12345,123456789 valid (must support only digit length 5 or 9)

Answer 1

Please try the following:

var lines = new []
{
    "09103,09101,",
    "09103,09101",
    "12345,1234567",
    "12345,123456789",
    "12345"
};

var re = new Regex(@"^\d{1,5}(,(\d{5}|\d{9}))?,?$");

foreach (var line in lines)
{
    Console.WriteLine("{0} = {1}", line, re.IsMatch(line) ? "Valid" : "Invalid");
}

Output

09103,09101, = Valid
09103,09101 = Valid
12345,1234567 = Invalid
12345,123456789 = Valid
12345 = Valid

You can run it here: C# Fiddle

Answer 2

Try this, for your exact test cases.

^\d{5},?$|^\d{5},\d{5},?$|^\d{5},\d{9},?$

It uses the | character to separate 'alternative' patterns, read it as "or". Ie

^\d{5}$  OR  ^\d{5},\d{5}$  OR  ^\d{5},\d{9}$

Answer 3

Just make the part which was preceded by comma to optional, so that it would match only 12345 or 12345,

^(?:\d{5}|\d{9})(?:,(?:\d{5}|\d{9}))?,?$

DEMO