using System;

using System.Collections.Generic;

using System.Text.RegularExpressions;

​

List<string> inputs = new()

{

    "Nick", // no match

    "Nick1", // no match

    "1Nick", // no match

    "Nick42", // match

    "42Nick", // match

    "4Nick2", // match

    "42", // match

    "1337", // match

    "6", // no match

};

​

string pattern = "[0-9]+[a-zA-Z]*[0-9]+";

Regex regex = new Regex(pattern);

​

foreach (var input in inputs)

{

    bool isMatch = regex.IsMatch(input);

    Console.WriteLine(

        $"'{input}' {(isMatch ? "did" : "did not")} " +

        "match the pattern.");

}