/* Author: Jiangong SUN */ Extension methods enable you to "add" methods to existing types without creating a new derived type, recompiling, or otherwise modifying the original type. Extension methods are a special kind of static method, but they are called as if they were instance methods on the extended type. The most common extension methods are in LINQ; Linq provides two classes: Enumerable and Queryable. And their extensions methods operate on IEnumerable<T> and IQueryable<T>. Extension methods are static methods who reside in static utility classes. For example: public static bool IsNull(this object x) { return x == null; } public static bool IsNullOrEmpty(this object text) { return text == null || (string)text == ""; } public static IEnumerable<int> GetOddMembers(this List<int> list) { return list.Where(x => x%2 != 0); } Usage: object y = null; Console.WriteLine(y.IsNull()); //True y = new object(); Console.WriteLine(y.IsNull()); //False object s = null; Console.WriteLine(s.IsNullOrEmpty()); //True s = string.Empty; Console.WriteLine(s.IsNullOrEmpty()); //True s = "hello"; Console.WriteLine(s.IsNullOrEmpty()); //False Console.WriteLine(IsObjectNull.IsNullOrEmpty(null)); //True List<int> list = new List<int>() {1, 2, 5, 7, 12}; var oddMembers = list.GetOddMembers(); foreach (var oddMember in oddMembers) { Console.WriteLine(oddMember); //1 5 7 } I Hope this can do help to you! Enjoy coding!
