regex for characters

Question

Hello,

In C# i'm using RegexValidator to validate a field which can contains only L,l,M,m,D,d values. I tried to use [RegexValidator("[l|L][M|m][D|d]" ... , but this does not work. Any ideas?

Thanks

Answer 1

This regex:

[l|L][M|m][D|d]

means:

• l, | or L; then
• M, | or m; then
• D, | or d.

Try:

^[LMD]+$

as a case insensitive match if you can do that or:

^[LlMmDd]+$

if you can't.

Both of these require the whole string to match a sequence of L, l, M, m, D or d characters. Use + to mean one or more if it can't be empty or * to mean 0 or more if it's allowed to be empty.

Edit: based on the updated information, if you want to allow one of those characters and only one of those then:

^[LlMmDd]$

Answer 2

If I understand you correctly then you can try something like this

var s1 = "Ll";
var s2 = "m";
var s3 = "LmD";
var pattern = "^[LMD]$";

Console.WriteLine( Regex.IsMatch(s1, pattern, RegexOptions.IgnoreCase) );
Console.WriteLine( Regex.IsMatch(s2, pattern, RegexOptions.IgnoreCase) );
Console.WriteLine( Regex.IsMatch(s3, pattern, RegexOptions.IgnoreCase) );

Writes the following to the console

False
True
False

You can only use Regex on string but you could always convert your char

char c = 'd';
Console.WriteLine( Regex.IsMatch(new String(c,1), pattern, RegexOptions.IgnoreCase));

Answer 3

You need to read up on regexp. You should be able to Google (or Bing) on tutorials of regexp.

[asdf] means one and only one and not less than one char which is either a, s, d or f.
[asdf]* means any number of characters but they must be either be a, s, d or f.
[asdf]+ means at least one character and they must either be a, s, d or f.

Regexp does not use the | character as an OR operator in within a [] square bracket character definition constraint.

[A-Z][a-z]+[0-9] means a String that must have the first character uppercase alphabet (any uppercase char between A to Z) followed by at least one lowercase alphabet (any lowercase char between a to z) and terminated by a decimal digit.

[l|L][M|m][D|d] means the string must have exactly 3 chars.
First char must be either l, | or L.
2nd char must be either M, | or m.
3rd char must be either D, | or d.

[lL][Mm][Dd] may be what you want to use.
[lLMmDd]+ for a string of at least one char constrained to be either l, L, M, m, D or d.
[lLMmDd][lLMmDd][lLMmDd]+ for a string of at least 3 chars long where all chars are constrained to be either l, L, M, m, D or d.

Answer 4

This code should read a string from the console, and match it. It should accept only 1 character, and matches with the characters you provided.

     static void Main(string[] args)
    {
        Regex regex = new Regex(@"^[L|M|D]$", RegexOptions.IgnoreCase);
        System.Console.WriteLine("Enter Text");
        String str = System.Console.ReadLine();
        Match match = regex.Match(str);

        if (match.Success == true)
        {
            System.Console.WriteLine("Success");
        }
        else
        {
            System.Console.WriteLine("Fail");
        }
        System.Console.ReadLine();
    }

Answer 5

you can also use inversion. check the field for characters not in your defined list.

/[^LlMmDd]+/