C#•14mo ago

✅ Default interface methods - Am I using them wrong?

I'm trying to learn when/where to properly use interfaces, and I don't understand why my default method doesn't work.

I have this:

c#
public interface IMyInterface {
    string Name { get; set; }
    string JobTitle { get; set; }
    
    void Foo() { Console.WriteLine("Default Foo"); }
}

public class Person {
    public string Name { get; set; }
}

public class Employee : Person, IMyInterface {
    public string JobTitle { get; set; }
}

c#
public interface IMyInterface {
    string Name { get; set; }
    string JobTitle { get; set; }
    
    void Foo() { Console.WriteLine("Default Foo"); }
}

public class Person {
    public string Name { get; set; }
}

public class Employee : Person, IMyInterface {
    public string JobTitle { get; set; }
}

c#
public interface IMyInterface {
    string Name { get; set; }
    string JobTitle { get; set; }
    
    void Foo() { Console.WriteLine("Default Foo"); }
}

public class Person {
    public string Name { get; set; }
}

public class Employee : Person, IMyInterface {
    public string JobTitle { get; set; }
}

c#
public interface IMyInterface {
    string Name { get; set; }
    string JobTitle { get; set; }
    
    void Foo() { Console.WriteLine("Default Foo"); }
}

public class Person {
    public string Name { get; set; }
}

public class Employee : Person, IMyInterface {
    public string JobTitle { get; set; }
}

Creating a new instance of

Employee

Employee

Employee

Employee should give me access to

employee.Foo()

employee.Foo()

employee.Foo()

employee.Foo(), but it doesn't.

Maybe I'm just overlooking something simple, but I don't understand :/

UnemployedNinjaOP•11/7/24, 5:57 PM

I'm using .net6

Jimmacle•11/7/24, 5:57 PM

you can only access DIMs by casting the object to the interface

Jimmacle•11/7/24, 5:57 PM

that being said, you shouldn't use DIMs for this

Jimmacle•11/7/24, 5:57 PM

they were added to the language mostly as a way to add new methods to interfaces in a backwards compatible way

UnemployedNinjaOP•11/7/24, 6:00 PM

So DIM's are generally not very good practice to use?

becquerel•11/7/24, 6:11 PM

they are a tool meant for things like authors of libraries

becquerel•11/7/24, 6:11 PM

not so much normal application code

UnemployedNinjaOP•11/7/24, 7:43 PM

!close

Accord•11/7/24, 7:43 PM

Closed!

✅ Default interface methods - Am I using them wrong?

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