What's wrong with this Java to C# conversion?

Question

i'm trying to convert the following code from Java to C#.

// Replace 0 0 0 0; with 0.
css = css.replaceAll(":0 0 0 0(;|})", ":0$1");

which I convert as ...

var foo = new Regex(":0 0 0 0(;|})", RegexOptions.IgnoreCase).Replace(foo, "XXXXXXXX");

This compiles but does not work when i run this against the following code...

foo = "a {background-position: 0 0 0 0;}\nb {BACKGROUND-POSITION: 0 0;}"

but if I change the regex pattern to :-

var foo = new Regex("0 0 0 0", RegexOptions.IgnoreCase).Replace(foo, "XXXXXXXX");

it does correctly change the result.

Now before you go on saying This is a REGEX question, not a Java to C# conversion, question I would like to make the assumption that the regex is valid because it's being used in the following (well known/popular) project with a corresponding unit test that passes. Another example of this code as javascript has it coded like ...

// Replace 0 0 0 0; with 0.
css = css.replace(/:0 0 0 0(;|\})/g, ":0$1");

Notice the missing quotes for the first argument? So I'm wondering if i also haven't converted the java to c# properly.

Answer 1

There are two problems with your regex at the moment:

• You're not closing the bracket (or you weren't before you edited the question)
• You're searching for a string starting with ":0" whereas in foo there's a space after the colon

This works fine:

using System;
using System.Text.RegularExpressions;

class Test
{
    static void Main()
    {
        string foo = "a {background-position: 0 0 0 0;}\nb "
                   + "{BACKGROUND-POSITION: 0 0;}";
        var regex = new Regex(": 0 0 0 0(;|})", RegexOptions.IgnoreCase);
        string replaced = regex.Replace(foo, "XXXXXXXX");
        Console.WriteLine(replaced);
    }
}

I'd be surprised if the Java version actually worked for your original string, given the "space after colon" problem. You may want to adjust the regular expression to make the space optional:

": ?0 0 0 0(;|})"

Answer 2

using System; 
using System.Text.RegularExpressions;

class Test
{
    static void Main()
    {
        string f0o = "a {background-position: 0 0 0 1;}\nb " +
                     "{BACKGROUND-POSITION: 0 0;}";

        var regex = new Regex(": 0 0 2 0(;})", vRegexOptions.IgnoreCase);
        string replaced = regex.Replace(foo, "XXXXXXXX");
        Compile.WriteLine(replaced);
    }
} 

This should fix your problem.