CODEWITHSUNDEEP
c#regex
Ofir
Ofir

Reputation: 5319

Simple string regular expression

I'm trying to write very simple regular expression - this world is entirely new for me so I need an help.

I need to validate the next pattern: starts with C0 and finish with 4 digits exactly for example:

C01245 - legal

C04751 - legal

C15821 - not legal (does not starts with 'C0')

C0412 - not legal (mismatch length)

C0a457 - not legal

I took "cheat sheet" and wrote the next pattern:

C0\A\d{4) which means (I think) : starts with C0 and continue with 4 digits but this pattern always return "false".

What wrong with my pattern?

Upvotes: 1

Views: 174

Answers (4)

Chandru
Chandru

Reputation: 336

Please take a look at this Snippet ,

using System.IO;
using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main()
    {
        string input1 = "C0123456"; 
        // input1 starts with C0 and ends with 4 digit , allowing any number of                 
        // characters/digit in between
        string input2 = "C01234";
        // input2 starts with C0 and ends with 4 digit , without                
        // characters/digit in between
        String pattern1=@"\b[C][0][a-z A-Z 0-9]*\d{4}\b";
        String pattern2=@"\b[C][0]\d{4}\b";
        Match m = Regex.Match(input1, pattern1);
        if(m.Success)
        Console.WriteLine("Pattern1 matched input1 and the value is : "+m.Value);
        m = Regex.Match(input2, pattern2);
        if(m.Success)
        Console.WriteLine("Pattern2 matched input2 and the value is : "+m.Value);
          m = Regex.Match(input1, pattern2);
        if(m.Success)
        Console.WriteLine("Pattern2 matched input1 and the value is : "+m.Value);
          m = Regex.Match(input2, pattern1);
        if(m.Success)
        Console.WriteLine("Pattern1 matched input2 and the value is : "+m.Value);


    }
}

Output:

Pattern1 matched input1 and the value is : C0123456

Pattern2 matched input2 and the value is : C01234

Pattern1 matched input2 and the value is : C01234

Upvotes: 0

jedmao
jedmao

Reputation: 10512

^C0\d{4,}$

The string must start ^ with C0, followed by 4 or more digits \d{4,} at the end of the string $.

Simply take off the last $ if it's not actually at the end of the string.

And if you're not looking to sandwich more numbers in-between, just remove the comma..

Kudos to @femtoRgon for the \d{4,} (see comments).

Upvotes: 1

Anirudha
Anirudha

Reputation: 32827

You have to use this regex

^C0\d{4}$

^ would mark the beginning of string

$ would mark the end of string

\d{4} would match 4 digits

You could also do it this way

if(input.StartsWith("C0") &&
   input.Length==6 && 
   input.Substring(2).ToCharArray().All(x=>Char.IsDigit(x)))
//valid
else //invalid

Upvotes: 3

David Hofmann
David Hofmann

Reputation: 5775

if you go to http://gskinner.com/RegExr/ you can write this expression:

^(C0[0-9]*[0-9]{4})[^0-9]

And in the content you put:

C012345 - legal
C047851 - legal
C*1*54821 - not legal (does not starts with 'C0')
C0412 - not legal (mismatch length)
C0*a*4587 - not legal

And you will see that it only matches what you want.

Upvotes: -1

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