Question

Im checking some strings with my regex and somehow its not perfect. Im not sure why. I would like to allow string with only these characters:

• A to Z
• 0 to 9
• .
• %
• /
• {space}
• +
• $

So I thought this regex should be enough:

Regex("[^A-Z0-9.$/+%\\- ]$")

But with some string its not really working. I made a small example:

    static Regex regex = new Regex("[^A-Z0-9.$/+%\\- ]$");

    static void Main()
    {
        string s;

        Console.WriteLine("check: \n");

        s = "?~=) 2313";
        Console.WriteLine(s + ": " +IsValid(s));

        s = "ÄÜÖ";
        Console.WriteLine(s + ": " + IsValid(s));

        s = "Ü~=) 2313";
        Console.WriteLine(s + ": " + IsValid(s));

        s = "Ü 2313";
        Console.WriteLine(s + ": " + IsValid(s));

        s = "~=) 2313 Ü";
        Console.WriteLine(s + ": " + IsValid(s));

        s = "ÜÜÜ";
        Console.WriteLine(s + ": " + IsValid(s));

        s = "~=)";
        Console.WriteLine(s + ": " + IsValid(s));

        s = "THIS--STRING $1234567890$ SHOULD BE VALID.%/ +";
        Console.WriteLine(s + ": " + IsValid(s));

        Console.ReadKey();
    }

    public static bool IsValid(string input)
    {
        if (regex.IsMatch(input)) return false;
        return true;
    }

As output I get:

The 1.,3. and 4. are True, but this is wrong. What is wrong with my regex? Any ideas? Thank you

Answer 1

It should be

^[A-Z0-9.$/+%\\- ]+$
|                 ||match end of the string
|                 |
|                 |match one or more characters of [A-Z0-9.$/+%\\- ]
|start of the string

You need to use quantifiers like +,* to match multiple characters

---

Your IsValid Class should be

public static bool IsValid(string input)
    {
        if (regex.IsMatch(input)) return true;
        return false;
    }