using regex to validate input formatting in C#

Question

This is a super basic question (I am brain dead today):

How do I validate in input using regexes, to see: 1) if the input is in a certain form 2) if the input is all caps (just casting the input to caps is not feasible for this)

I want ot make sure my inputs are in the form XX_XX. Here isi what I have:

public bool IsKosher(string input)
{
    Regex r = new Regex(input);
    if(r.Matches([A-Z]_[A-Z]))
    {
        return true;
    }
    return false;     
}

Any ideas why it's not compiling?

Thank you!

Sergey Kalinichenko · Accepted Answer · 2012-05-22 19:57:28Z

5

You are missing double quotes, you put parameters in wrong places, and you do not need an if statement:

public bool IsKosher(string input) {
    return Regex.IsMatch(input, "[A-Z]{2}_[A-Z]{2}");
}

answered May 22, 2012 at 19:57

Sergey Kalinichenko

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Comments

Austin Salonen · Accepted Answer · 2012-05-22 20:00:37Z

3

Quotes? A missing closing parenthesis? Matches not returning a boolean? Swapping string parameters? All will cause your code not to compile.

Though you may want this if it is "XX_XX":

var r = new Regex("[A-Z]{2}_[A-Z]{2}");
return r.IsMatch(input);

edited May 22, 2012 at 20:00

answered May 22, 2012 at 19:54

Austin Salonen

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Comments

Erwin · Accepted Answer · 2012-05-22 19:55:59Z

2

You have to put [A-Z]_[A-Z] between quotes like this:

if(r.Matches("[A-Z]_[A-Z]")

answered May 22, 2012 at 19:55

Erwin

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Comments

Douglas · Accepted Answer · 2012-05-22 20:02:43Z

2

Quotes.
Two characters on either side of the _.
The Regex constructor takes the pattern; the Matches method takes the string to search.
The Matches method returns a MatchCollection. IsMatch returns a boolean.

Like so:

if (Regex.IsMatch(input, "[A-Z]{2}_[A-Z]{2}")

edited May 22, 2012 at 20:02

answered May 22, 2012 at 19:56

Douglas

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