C# 擴(kuò)展方法

public static class StringExtension {
   public static bool IsCapitalized (this string s) {
      if (string.IsNullOrEmpty(s))
         return false;
      return char.IsUpper (s[0]);
   }
}

Console.WriteLine ("Javascript".IsCapitalized());

Console.WriteLine (StringExtension.IsCapitalized ("Javascript"));

public static T First<T> (this IEnumerable<T> sequence){
    foreach (T element in sequence)
        return element;
    throw new InvalidOperationException ("No elements!");
}
...
Console.WriteLine ("Javascript".First()); // J

class Main {
   public void MyMethod (object x) { } 
}

static class Extensions {
   public static void MyMethod (this Main t, int x) { }
}

Extensions.MyMethod(...)

static class StringExtension {
    public static bool IsCapitalized (this string s) {...}
}
static class ObjectHelper {
    public static bool IsCapitalized (this object s) {...}
}

bool test1 = "Javascript".IsCapitalized();

bool test2 = (ObjectHelper.IsCapitalized ("Javascript"));