如何在C＃中使用正则表达式匹配规则

Question

I am new to regex stuff in C#. I am not sure how to use the regex to validate client reference number. This client reference number has 3 different types : id, mobile number, and serial number.

C#:

string client = "ABC 1234567891233";

//do code stuff here:
if Regex matches 3-4 digits to client, return value = client id
else if Regex matches 8 digts to client, return value = ref no
else if Regex matches 13 digits to client, return value = phone no

I dont know how to count digits using Regex for different types. Like Regex("{![\\d.....}").

Answer 1

I don't understand why you're bent on using regular expressions here. A simple one-liner would do, eg. even such an extension method:

static int NumbersCount(this string str)
{
    return str.ToCharArray().Where(c => Char.IsNumber(c)).Count();
}

It's clearer and more maintainable in my opinion.

You could probably give it a go with group matching and something along the lines of

"(?<client>[0-9]{5,9}?)|(?<serial>[0-9]{10}?)|(?<mobile>[0-9]{13,}?)"

Then you'd check whether you have a match for "client", "serial", "mobile" and interpret the string input on that basis. But is it easier to understand?

Does it express your intentions more clearly for those reading your code later on?

If the requirement is such that these numbers must be consecutive (as @Corak points out)... I'd still write that iteratively, like so:

/// <summary>
/// returns lengths of all the numeric sequences encountered in the string
/// </summary>        
static IEnumerable<int> Lengths(string str)
{
    var count = 0;
    for (var i = 0; i < str.Length; i++)
    {
        if (Char.IsNumber(str[i]))
        {
            count++;
        }
        if ((!Char.IsNumber(str[i]) || i == str.Length - 1) && count > 0)
        {
            yield return count;                
            count = 0;                    
        }
    }
}

And then you could simply:

bool IsClientID(string str)
{
    var lenghts = Lengths(str);
    return lenghts.Count() == 1 && lenghts.Single() == 5;            
}

Is it more verbose? Yes, but chances are that people will still like you more than if you make them fiddling with regex every time the validation rules happen to change, or some debugging is required : ) This includes your future self.

Answer 2

I'm not sure if I understood your question. But if you want to get the number of Numerical Characters from a string you can use the following code:

Regex regex = new Regex(@"^[0-9]+$");
string ValidateString = regex.Replace(ValidateString, "");
if(ValidateString.Length > 4 && ValidateString.Length < 10)
    //this is a customer id
....