Possible to extend the String class in .net

Question

How to override or extend .net main classes. for example

public class String
{
    public boolean contains(string str,boolean IgnoreCase){...}
    public string replace(string str,string str2,boolean IgnoreCase){...}
}

after

string aa="this is a Sample";
if(aa.contains("sample",false))
{...}

is it possible?

Answer 1

The String class is sealed so you can't inherit from it. Extension methods are your best bet. They have the same feel as instance methods without the cost of inheritance.

public static class Extensions {
  public static bool contains(this string source, bool ignoreCase) {... }
}

void Example {
  string str = "aoeeuAOEU";
  if ( str.contains("a", true) ) { ... }
}

You will need to be using VS 2008 in order to use extension methods.