Question

I want to do some regex.match by building the pattern dynamically. The following code is not working. I was wondering how can I convert the string “^[ABCDEFG][ABCDEFG]$” to @”^[ABCDEFG][ABCDEFG]$” and use it for regex.

Thanks

static string Convert(string s)
    {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.Length; i++)
        {
            if (s[i].Equals('N'))
            {
                sb.Append("[ABCDEFG]");
            }
            else
            {
                sb.Append(s[i]);
            }
        }
        return sb.ToString();
    }



    static void Main(string[] args)
    {
        string seq = "CA";
        Regex re = new Regex(Convert("^NN$"));
        if (re.Match(seq).Success)
        {
            Console.WriteLine("match");
        }



        Console.ReadKey();
    }

Answer 1

A verbatim string (string literal prefixed with a @) is only sytactic sugar to allow simpler file system access and regular expression writing, because in verbatim strings the character \ isn’t treated as an escape character. That way you don’t have to write "\\\\\\.\\\\" to match the string "\.\" in a regex but only @"\\\.\\" which is less prone to error because counting the backslashes becomes easier as their number decreases.

The following example will prove that verbatim strings are no different from normal ones:

public class Program
{
    public string GetString(bool verbatim)
    {
        if(verbatim)
        {
            return @"this is a test";
        }
        else
        {
            return "this is a test";
        }
    }

    public static void Main(string[] args)
    {
        var verbatim = GetString(true);
        var normal = GetString(false);

        // should print 'true', if I'm not mistaken, because of string interning
        Console.WriteLine("Reference equals:" + ReferenceEquals(verbatim, normal));

        // will definitely print 'true'
        Console.WriteLine("Equals:" + verbatim.Equals(normal));
    }
}