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c#interface

Calling method of concrete class which implemets interface

I have an interface :

public interface IHello {}

I have 2 classes :

public class A : IHello
{
    public void Method1()
    {
        ...
    }
}

public class B : IHello
{
}

When I make a call to Method1(), I get the following error :

public class C
{
    private IHello obj123;
    static void Main() 
    {
        obj123 = new A();
        obj123.Method1();  // Method1 does not exist in IHello
    }
}

I understand that obj123 is of type IHello. I want to do something like (GetTypeof(Ihello)).Method1 exists? Then call

How to achieve this?

Solution 
  • if (obj123 is A a)
{
    a.Method1();
}

    Please note that this type of selectively casting is often seen as bad OOP design. You should probably not rely on it too much and instead find a design where this isn't neccessary.