C# Replace with Callback Function like in AS3

Question

In AS3 you have a function on a string with this signature:

function replace(pattern:*, repl:Object):String

The repl:Object can also specify a function. If you specify a function, the string returned by the function is inserted in place of the matching content.

Also, is it possible to get the the original string in which I want to replace things?

(In AS3 you can get the original string by

var input:String = arguments[2]; //in the callback function

)

I don't see a property in the Match class containing the original string...

Marc Gravell · Accepted Answer · 2009-01-14 08:16:23Z

13

static void Main() {

    string s1 = Regex.Replace("abcdefghik", "e",
        match => "*I'm a callback*");

    string s2 = Regex.Replace("abcdefghik", "c", Callback);
}
static string Callback(Match match) {
    return "*and so am i*";
}

Note you have access to the matched data via the argument (and match.Value in particular, unless you want access to the regex groups (.Groups) etc).

answered Jan 14, 2009 at 8:16

Marc Gravell

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1 Comment

Lieven Cardoen Over a year ago

Is it possible to get the the original string in which I want to replace things? (In AS3 you can get the original string by var input:String = arguments[2]; //in the callback function ) I don't see a property in the Mach class containing the original string...

Konrad Rudolph · Accepted Answer · 2009-01-14 08:12:46Z

6

In order to do this in C#, use System.Text.RegularExpressions.Regex.Replace() which takes a callback.

answered Jan 14, 2009 at 8:12

Konrad Rudolph

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Jon Skeet · Accepted Answer · 2009-01-14 08:32:48Z

5

Just as an example to make the existing answers absolutely concrete, and showing how lambda expressions can be handy:

using System;
using System.Text.RegularExpressions;

class Test
{
    static void Main()
    {
        var template = "On $today$ you need to do something.";
        var regex = new Regex(@"\$today\$");
        var text = regex.Replace(template,
            match => DateTime.Now.ToString("d"));
        Console.WriteLine(text);
    }
}

(Marc's answer appeared while I was writing this, but I'll leave it up as a complete example unless anyone thinks it's just redundant. I'm happy to delete it if suggested.)

edited Jan 14, 2009 at 8:32

answered Jan 14, 2009 at 8:17

Jon Skeet

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