Question

I require a regex that will text that a string starts with one chaecter (a-z) and is followed by at least one digit.

I have tried…

^[a-zA-Z]{1}\d+

my test data is…

a1234 (pass)
B123444434 (pass)
Z098745 (pass)
ZZ12345 (fail)
G4b553b3 (fail)

The problem is that the last two lines shoudl fail but dont, Im not sure if the problem is my regex or my c# (below);

    int pass = 0;
    int fail = 0;

    string[] testdata = 
    {
        "a1234", 
        "B1234", 
        "Z098745", 
        "ZZ12345", 
        "G4b5533", 
    };

    string sPattern = "[a-zA-Z]{1}\\d+";

    foreach (string s in testdata)
    {
        if (System.Text.RegularExpressions.Regex.IsMatch(s, sPattern))
        {
            pass++;
        }
        else
        {
            fail++;
        }
    }

Answer 1

You seem to have missed ^ in your code, so Z12345 matches for ZZ12345 and b5533 matches for G4b5533.

And as it was mentioned, {1} is redundant.

I believe you should have

string sPattern = "^[a-zA-Z]\\d+$";

in your code.