How can i add a method to mscorelib

Question

I want to add some methods to mscorlib. For example:

string abc;

abc.IsNumeric()

i hope could explain my question.

Answer 1

You can't add methods to mscorlib, however you can use extension methods so they appear as if they are defined on string, e.g.

public static class StringExtensions
{
    public static bool IsNumeric(this string s)
    {
        // TODO
    }
}

Which you can then call as you requested, e.g.

"1234".IsNumeric()