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Yyds dry goods inventory override and virtual of classes in C

2022-07-04 01:49:00 【Andy ahui】

Welcome to be my reader , I hope this article can give you some help .

Preface

I learned class derivation with you yesterday , Know the difference between derived class and base class .

Today, let's look at how the virtual methods and override methods of derived classes and base classes are used .

When we use base class references to access derived class objects , You get members of the base class . When using virtual methods , You can get the members and functions of the derived class .

 class Ahui:InfoBase
 {
     public string Name = " aunt ";
          
     public string GetInfo() 
     {
         return this.Name+""+this.Age;
     }
 
 class InfoBase 
 {
     public int Age=27;
     public string Name = "ahui" 
     public string GetInfo() 
     {
         return Name;
      
     public string Love() 
     {
         return " Woman ";
     }
 }

     
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The above code is a simple expression of base and derived classes , We try to pass the base class InfoBase To access derived classes Ahui The methods inside are shown in the output above .

 static void Main(string[] args)
 {
     Ahui hui = new Ahui();
     InfoBase info = (InfoBase)h
     Console.WriteLine(hui.GetInfo());
     Console.WriteLine(info.GetInfo());
     Console.ReadKey();
  }

     
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#yyds Dry inventory # C# Middle class override and virtual_ overwrite

From the above picture, you can see the access to... Through their respective instances GetInfo() Method returns different values , The base class returns its own , The derived class returns its own .

So when we want to use the reference of the base class to access the derived class object , Virtual methods can be used to access .

It must meet the following conditions ：

The method of the derived class and the method of the base class have the same signature and return type .
The methods of the base class use virtual mark .
Methods of derived classes use override mark .

 class Ahui:InfoBase
 {
     public string Name = " aunt ";
          
     public override string GetInfo() 
     {
         return this.Name+""+this.Age;
     }
     
 class InfoBase 
 {
     public int Age=27;
     public string Name = "ahui"     public virtual string GetInfo() 
     {
         return Name;
          public string Love() 
     {
         return " Woman ";
     }
 }

     
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#yyds Dry inventory # C# Middle class override and virtual_ Virtual method _02

Compare with the last output picture , You can see that when using virtual methods and overriding tags , All the output are members of derived classes .

It should be noted that ：

Overridden and overridden methods must have the same accessibility .
Cannot override static Method or non virtual method .
Method 、 Properties and indexers 、 Member type events can be declared as virtual and override.