Question

I need to have a multiple Form classes in my project. So was thinking about putting everything those forms will have in common, together in abstract class. This class will have inheriet Form class and also an interface. Sth like that:

public interface IMyForm
{
void Init();
}

public abstract class AMyForm : Form, IMyForm
{
    void IBrowser.Init()
    {
        throw new NotImplementedException();
    }     
}

public partial class MainClass : AMyForm 
{

// But here the warning is shown (That i have to add override keyword),
// but when i do, The error is shown that i cannot override from non abstract thing 
    public void Init() 
    {
    }
}

Could u tell me how to achieve that ?

Answer 1

You just want to not use explicit interface implementation in your abstract class:

public abstract class AMyForm : Form, IMyForm
{
    public virtual void Init()
    {
        throw new NotImplementedException();
    }     
}

Or just make it abstract:

public abstract class AMyForm : Form, IMyForm
{
    public abstract void Init();
}

In both cases, you then just override it in your concrete class.

Alternatively, if you really want to use explicit interface implementation in your abstract class, you should use it again in your concrete class:

public partial class MainClass : AMyForm, IMyForm
{
    void IMyForm.Init() 
    {
        // Stuff
    }
}

The downside is that any subclass of AMyForm which doesn’t do this will basically have the broken IMyForm implementation. Using the first approach is better here.

EDIT: Or, as per supercat’s suggestion:

public abstract class AMyForm : Form, IMyForm
{
    void IBrowser.Init()
    {
        InitImpl();
        // And anything else you need...
    }     

    // Or abstract...
    protected virtual void InitImpl()
    {
    }
}

Then override InitImpl in your concrete class.