[. Net Study Notes] C # new features-generic

Generic Overview

 

C # generics are called type parameters. Generic key points:

• In the definition method, the value of a variable is usually used as a parameter, but the type of the variable itself can also be used as a parameter.
• The generic type allows you to specify the type parameter when calling it.
• In. net, generics bring us three obvious advantages: type security,CodeReuse, reduce packing, and unpack operations.
• You can define a type security class through the generic type without compromising the type security, performance, or work efficiency.
• It can be declared and used in any type.
• Use parentheses to enclose general type parameters.

Several examples of the benefits of generics:

 Public   Class  Generic {  //  Non-generic: insecure type-errors cannot be found during compilation  //  Execution prompt: system. invalidcastexception: the specified conversion is invalid.          Public  Void  Showvalues1 () {arraylist list = New  Arraylist (); list. Add (  44  ); List. Add (  "  String  " ); //  Compiled              Foreach ( Int I In List) {console. writeline (  "  Output value:  " + I );}}  //  Generic: type security-Type Mismatch found during compilation          Public   Void  Showvalues2 () {list < String > List = New List < String >(); List. Add (  44 ); //  -- Compilation Error List. Add ( "  String  "  );  Foreach ( String S In  List) {console. writeline (  "  Output value:  " + S );}}  //  Non-generic: explicit type conversion is required, resulting in performance loss.          Public   Void  Showvalues3 () {arraylist list = New  Arraylist (); list. Add (  44  );  Int I = ( Int ) List [ 0  ]; Console. writeline ( "  Output value:  " + I );}  //  Generic: the type is determined during use, and no type conversion is required.          Public   Void  Showvalues4 () {list < Int > List = New List < Int > (); List. Add (  44 );  Int I = list [ 0  ]; Console. writeline (  "  Output value:  " + I );}} 

 

Custom generic and call. We can see the role of generics in code reuse.

 //  Customize a generic class      Public   Class Mygeneric <t> {  Public  Void  Showvalues (t a) {console. writeline (  "  Output value:  " + A. tostring ());}}  //  Use different types of parameters to call custom generics      Public   Class  Test_mygeneric {  Public   Void  Test_int_showvalues () {mygeneric <Int > Fanxing = New Mygeneric < Int > (); Fanxing. showvalues (  100  );}  Public   Void  Test_string_showvalues () {mygeneric < String > Fanxing = New Mygeneric < String >(); Fanxing. showvalues (  "  Hello  "  );}  Public   Void  Test_doube_showvalues () {mygeneric < Double > Fanxing = New Mygeneric < Double > (); Fanxing. showvalues (  3.14 );}  //  Define a generic method: Exchange two variables          Public   Void Swap <t> ( Ref T, Ref  T B) {T temp; temp = A; = B; B = Temp ;}  //  Exchange integer          Public  Void  Testswap1 (){  Int T = 1  ;  Int G = 2  ; Swap (  Ref T, Ref  G); console. writeline (  "  Output value T:  " +T. tostring (); console. writeline (  "  Output Value G:  " + G. tostring ());}  //  Exchange string          Public   Void  Testswap2 (){  String T = "  Str1  "  ; String G = "  Str2  "  ; Swap (  Ref T, Ref  G); console. writeline (  "  Output value T:  " + T. tostring (); console. writeline (  "  Output Value G:  " +G. tostring ());}  //  Exchange object          Public   Class  Usrentity {  Public   String Username { Get ; Set  ;}  Public   String Sex { Get ; Set ;}}  Public   Void  Testswap3 () {usrentity t = New Usrentity () {username = "  James  " , Sex = "  Male  "  }; Usrentity g = New Usrentity () {username = " Xiaohong  " , Sex = "  Female  "  }; Swap (  Ref T, Ref  G); console. writeline (  "  Output value T:  " + T. username + "  :  " +T. Sex); console. writeline (  "  Output Value G:  " + G. username + "  :  " + G. Sex );}} 

 

Note: This article is based on the relevant training materials.