Generics in. Net

Generics defer the determination of the type of a class or method until the class or method is instantiated, that is, the first declaration is not specifying a type, and then specifying the type when it is used (instantiated)

Generics can be used for classes, methods, delegates, events, and so on

Let's write a simple generic type

 Public class Genericclass<t>{          void  somemethod (  t   t  )          {                   // do something          }}

Here's how to use it:

Instantiate a class

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1	GenericClass<int> gci=newGenericClass<int>();

Method SomeMethod has an integer-type parameter.

Write an example below

usingSystem;usingSystem.Collections.Generic;usingSystem.Text;namespaceexample{classGenericclass<t>    {         Public voidPrinttype (T t) {Console.WriteLine ("value:{0} type:{1}", T,t.gettype ()); }    }    classProgram {Static voidMain (string[] args) {            inti =0; Genericclass<int> GCI =Newgenericclass<int>(); Gci.            Printtype (i); strings ="Hello"; Genericclass<string> GCS =Newgenericclass<string>(); Gcs.            Printtype (s);        Console.ReadLine (); }    }}

a generic method can appear on a generic or non-generic type. It is important to note that the method is a generic method, not as long as the method belongs to a generic type, or even if the type of the method's formal parameter is a generic parameter of the enclosing type. A method can be called a generic method only if it has its own type parameter list. In the following code, only method G is a generic method.

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class A {     T G<T>(T arg) {...} } class Generic<T> {     T M(T arg) {...}}

Where of generics

The where of generics can be qualified for type parameters. There are several ways to do this.

The where t:struct restriction type parameter T must inherit from System.ValueType.
　
The where T:class restriction type parameter T must be a reference type, that is, cannot inherit from System.ValueType.

where t:new () restriction type parameter T must have a default constructor

The where T:nameofclass restriction type parameter T must inherit from a class or implement an interface.

These limits can be combined, for example: public class point where T:class, IComparable, New ()

For example:

 class  person<t>  where  t:class   {}  " Span style= "Color:rgb (0, 0, 255); >class   program { static void  Main (string  Span style= "Color:rgb (0, 0, 0); >[] (args) {person  <int  > bb = new  person<//  error 1 type "int" must be a reference type to be used as a parameter in the generic type or method "Consoleapplication1.person<t>" T " }}