C＃在正则表达式中匹配字母，数字和特殊字符

Question

I have the following Regex :

[A-Z]{2}[0-9]{4}

and it matches perfectly with a string like this: AB1234 . But I have to improve this Regex to match with these specific rules:

• The string must have only two sharps (##) between each group ( AB1234##AB1234 )
• It may have 8 groups of string ( AB1234##AB1234##AB1234##AB1234##AB1234##AB1234##AB1234##AB1234 )
• Regardless the number of groups, the last one cannot have the sharps (##) at the end. So, if I have 3 groups, it will looks like this: AB1234##AB1234##AB1234

If I use the sample string from the second bullet point, my Regex will match with the pattern, but in this case it doesn't validade the characters between each group.

Can anyone help me to improve this Regex?

Answer 1

尝试这个：

^([A-Z]{2}[0-9]{4}##){0,7}([A-Z]{2}[0-9]{4})$

Answer 2

([A-Z]{2}[0-9]{4}##){0,7}([A-Z]{2}[0-9]{4})

Answer 3

You can combine Regex and LINQ then use an extension method like this:

public static bool Validate(this string source)
{
    string pattern = "[A-Z]{2}[0-9]{4}";
    return !source.StartsWith("##") &&
           !source.EndsWith("##") &&
           source.Split(new[] {"##"}, StringSplitOptions.RemoveEmptyEntries)
                 .All(x => Regex.IsMatch(x, pattern));
}

Usage:

bool t1 = "AB1234##AB1234".Validate(); // true
bool t2 = "AB1234##AB1234##AB1234".Validate(); // true
bool t3 = "AB1234##AB1234##" // false

Answer 4

^(?:[A-Z]{2}[0-9]{4})(?:##(?:[A-Z]{2}[0-9]{4})){0,7}$
    ^^^^^^^^^^^^^^^^    ^^^^^^^^^^^^^^^^^^^^^   ^^^
          (1)                    (2)            (3)

1. Match at least one string that begins with two capital letters that is followed by 4 decimal digits.
2. Optionally follow that from zero to 7 times by ## and a repetition of the first match.

Result: ( * indicates a match)

* AB1234
  AB1234x
* AB1234##AB1234
* AB1234##AB1234##AB1234
  AB1234##AB1234##AB1234x

See the live demo .

Note: This answer is quite similar to this other answer . However, the answer here begins with the assumption that at least one sequence of AB1234 is present. And it then allows for the possibility that it is followed zero to 7 times by ##AB1234 . In the end, both regex expressions are fine. It comes down to personal preference.

Also note that I used non-capturing groups (?:...) to avoid the unnecessary overhead of creating capture groups that aren't needed in this situation. (Capture groups are also known as back-references.)