C # where generic constraints and new

Recently inadvertently saw: Http://msdn.microsoft.com/zh-cn/library/bb384067.aspx. But, people stupid ah, Wood has to understand what the meaning of the end, wood approach to write a try it, right as a note

Examples are as follows:

Interface:

Using system;using system.collections.generic;using system.linq;using system.text;namespace WhereTest{//    < summary>    ///fruit interface///</summary> public interface ifruit    {        //fruit name        string fruitname        {            get;            Set;        }        String GetName ();        The/* interface can contain only declarations of methods, properties, indexers, and events.         * It is not allowed to declare modifiers on members, even PUBILC, because interface members are always public and cannot be declared as virtual and static.         * If modifiers are required, it is best to have the implementation class declared.        */    }}

Interface implementation:

Using system;using system.collections.generic;using system.linq;using system.text;namespace WhereTest{//    < summary>        ///Pear class///</summary> public class Peach:ifruit {//No parameters, common constructors        Peach ()        {        }        private string fruitname;        String Ifruit.fruitname        {            get            {                return this. ToString ();;            }            Set            {                fruitname = value;            }        }        String Ifruit.getname ()        {            return string. IsNullOrEmpty (fruitname)? "Wood has a name to find": Fruitname;}}    

Create a class with a generic constraint:

Using system;using system.collections.generic;using system.linq;using system.text;namespace WhereTest{//    < summary>///    classes with generic constraints///</summary>//    <typeparam name= "T" ></typeparam>    public class fruitmarket<t>        where T:ifruit,        new ()//new () means that this T must have the public constructor    {        T item = new T ( );         public void Fruitsayhello ()        {            item. Fruitname = "I am a pear";            Console.WriteLine ("Hello:" + string.) Format ("fruit:{0}", item. GetName ()));            Console.readkey ();        }        /* When defining a generic class, you can impose restrictions on the type types that client code can use for type parameters when instantiating a class.         * If the client code attempts to instantiate a class using a type not allowed by a constraint, a compile-time error occurs. */    }}

Because of the generic constraints of the WHERE clause, when you create an Fruitmarket object, the type of T can only be a class that inherits from the Ifruit interface.

Using system;using system.collections.generic;using system.linq;using system.text;namespace WhereTest{    class Program    {        static void Main (string[] args)        {            //instantiation can only invoke the corresponding method in the static method, otherwise the peach variable            is not found at all fruitmarket<peach> Peach = new fruitmarket<peach> ();            Peach. Fruitsayhello ();}}}    

Operation Result:

C # where generic constraints and new