Constructor, destructor, base, this

Constructor and destructor:

 
Using system; Class myclass {private int fnum; Public int num {get {return fnum ;}}/* the constructor has no return value, the default */Public myclass () {This. fnum = 2009;}/* can have multiple constructors with different parameters */Public myclass (int x) {This. fnum = x;} public myclass (Params int [] ARR) {foreach (int I in ARR) This. fnum + = I;}/* The Destructor has no parameters, no return values, no access modifier, and can only have one */~ Myclass () {// destructor is automatically called} class program {static void main () {myclass obj1, obj2, obj3; obj1 = new myclass (); console. writeline (obj1.num); // 2009 obj2 = new myclass (100); console. writeline (obj2.num); // 100 obj3 = new myclass (1, 2, 3); console. writeline (obj3.num); // 6 console. readkey ();}}

   
 
 
If there is no constructor or destructor, the default (or inheritance) will be used for new. A private constructor can prevent the class from being instantiated:
 

  
   
 
Using system; Class myclass {private myclass () {} public static void msg1 () {console. writeline ("msg1");} public static void msg2 () {console. writeline ("msg2") ;}} class program {static void main () {myclass. msg1 (); // msg1 myclass. msg2 (); // msg2 console. readkey ();}}

    
 
 
If a class has a non-default constructor, you cannot use the default constructor:
 

   
    
  
 
Using system; Class myclass {private int fnum; Public int num {get {return fnum ;}} public myclass (int x, int y) {This. fnum = x + y ;}} class program {static void main () {myclass OBJ; OBJ = new myclass (1, 2); console. writeline (obj. num); // 3 console. readkey ();}}

     
 
 
Static constructor:
 
 
The static constructor has no access modifier or parameter;
The static constructor is automatically called before new or any static member is called;
Static constructors are generally used to initialize static data;
A static constructor is triggered before the first new or first use of a static member;
Static constructor cannot be called directly.
 

    
     
   
Using system; Class myclass {public static int num; public static void shownum () {console. writeline (Num);} public void MSG () {console. writeline ("MSG");} static myclass () {num = 123 ;}} class program {static void main () {myclass. shownum (); // 123 myclass. num= 2009; myclass. shownum (); // 2009 myclass obj1 = new myclass (); obj1.msg (); // MSG console. readkey ();}}

      
 
 
Automatically call the constructor of the parent class:
 

     
      
    
Using system; Class Parent {public parent () {console. writeline ("parent") ;}} class Child1: parent {public Child1 () {console. writeline ("Child1");} public Child1 (int x) {console. writeline (x) ;}} class child2: Child1 {public child2 () {console. writeline ("child2");} public child2 (int x, int y) {console. writeline (x + y) ;}} class program {static void main () {parent P = new parent (); // parent Child1 C1 = new Child1 (); // parent/Child1 child2 C2 = new child2 (); // parent/Child1/child2 Child1 C11 = new Child1 (999 ); // parent/999 child2 c22 = new child2 (111,222); // parent/Child1/333 console. readkey ();}}

       
 
 
Base:
 

      
       
     
Using system; Class Parent {public parent () {console. writeline ("parent");} public parent (int x, int y) {console. writeline (x + y);} public parent (string S1, string S2) {console. writeline (S1 + S2) ;}} class Child1: parent {public Child1 () {console. writeline ("Child1") ;}} class child2: parent {public child2 (): Base () {console. writeline ("child2") ;}} class Child3: parent {public Child3 (): Base (111,222) {console. writeline ("Child3") ;}} class Child4: parent {public Child4 (): Base ("111", "222") {console. writeline ("Child4") ;}} class program {static void main () {Child1 C1 = new Child1 (); // parent/Child1 child2 C2 = new child2 (); // parent/child2 Child3 C3 = new Child3 (); // 333/Child3 Child4 C4 = new Child4 (); // 111222/Child4 console. readkey ();}}

        
 
 
This:
 

       
        
      
Using system; Class myclass {private string FS = "ABC-"; Public myclass () {console. writeline ("myclass");} public myclass (string Str) {console. writeline (this. FS + Str);} public myclass (INT num): this () {console. writeline (Num);} public myclass (int x, int y): This ("XYZ") {console. writeline (x + y) ;}} class program {static void main () {myclass C1 = new myclass (); // myclass C2 = new myclass ("EFG "); // ABC-EFG myclass C3 = new myclass (123); // myclass/123 myclass C4 = new myclass (111,222); // ABC-XYZ/333 console. readkey ();}}

         
 
 
Constructors, attributes, and base:
 

        
         
       
 
 using system; abstract class parent {private byte FID; Public parent (byte n) {FID = N ;} public byte ID {get {return FID;} set {FID = value ;}}} class child: parent {public child (byte myid): Base (myid) {}} class program {static void main () {Child rect = new child (6); console. writeline (rect. ID); // 6 rect. id = 8; console. writeline (rect. ID); // 8 console. readkey () ;}