C#

bashiwala wrote:

I understand that String is a class and string is a premetive type,

using BaseType = System.UInt32; // Allowed
using BaseType = uint; // Invalid!

// Allowed
public enum foo : uint {
    ...
}
// Invalid!
public enum foo : System.UInt32 {
    ...
}

Skippums wrote:

the using statement

namespace System
{
    public static class CharExtensionMethods
    {
        public static bool IsDigit(this char c, string str, int i, int n)
       {
            // Checks n chars starting from i in str if they are digits
            /* note that here you can get a reference to the character object you're dealing with through the c parameter */
       }
    }
}

using System;
using PooreDesign.ExtensionMethods;

namespace ConsoleApplication1
{
    static class Program
    {
        [STAThread]
        private static void Main(string[] args)
        {
            bool isDigit = char.IsDigit(args[0], 0, 5);
       }
    }
}