Example of Calling Interface in Derived Class and External Class in C#

This article describes the calling methods of C# interfaces in derived classes and external classes. Shared for everyone's reference, as follows:

C# interfaces are created using the interface keyword. Interfaces can include properties, methods, and other member variables. Derived classes of an interface can implement methods from the interface. A class can inherit multiple interfaces to implement methods from these interfaces, and an interface can also derive multiple classes. Methods in an interface can be directly called in the derived class.

Example of calling in derived class:

//Interface
public interface IPersonalService
{
   //Method in interface
   PersonalDTO QueryByUid(int uId);
}
//Derived class of interface
public class PersonalService : IPersonalService
{
    //Implementing interface method in derived class--Implicit implementation
    public PersonalDTO QueryByUid(int uId)
    {
      return _dal.QueryByUid(uId);
    }
    //Invoking interface method in derived class
    public void GetInfo(int userId)
    {
      //Calling method one
      IPersonalService p = new PersonalService();
      PersonalDTO dto = p.QueryByUid(userId);
      //Method Two
      PersonalService p2 = new PersonalService();
      IPersonalService p3 = (IPersonalService)p2;
      PersonalDTO dto = p3.QueryByUid(userId);
    }
}

When calling a method of an interface in an external class, first reference the namespace where the interface is located, and the subsequent steps are the same as calling in the derived class of the interface.

You can also call the interface by declaring an interface type property after referencing the namespace where the interface is located in the external class, as follows.

public IPersonalService pService{get;set;}
public void getInfo()
{
    pService.getInfo();
}

Readers who are interested in more C# related content can check the special topic of this site: 'C# Data Structures and Algorithms Tutorial', 'C# Traversal Algorithm and Technique Summary', 'C# Thread Usage Technique Summary', 'C# Common Control Usage Tutorial', 'WinForm Control Usage Summary', 'C# Array Operation Technique Summary', and 'C# Object-Oriented Programming Tutorial'.

I hope the content described in this article will be helpful to everyone in designing C# programs.

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