How to derive two abstract classes in C#

Question

I have app structure -

public abstract class a 
{
}
//defined in a.dll
public abstract class b
{
}
//defined in b.dll

//Above 2 DLL reference added in main project where I want to derive both of this abstract classee like

public abstract class proj : a, b
{
}

I am able to derive any one of it only not both. So pls guide me on missing things or wrong coding I had done.

Solution 1

You can't multiple inherit using C#. You can however achieve this by using an interface.

public interface Ia 
{

}

public interface Ib 
{

}

public abstract class MainProject : Ia, Ib  
{

}

C# interfaces only allow signatures of methods, properties, events and indexers. You will have to define the implementation of these in the proj (MainProgram) class.

Solution 2

public abstract class proj : a, b

This can't be done. C# doesn't allow multiple inheritance.

Solution 3

Rather than deriving from multiple abstract classes (which is illegal in C#), derive from two interfaces, (which are abstract by definition).

Solution 4

You can't derive from two classes at the same time. You should use interfaces instead.

public interface IFirstInterface
{
}
public interface ISecondInterface
{
}

public abstract class Proj : IFirstInterface, ISecondInterface
{
}

Now classes that inherit from Proj will still need to implement all methods and properties defined in both interfaces.

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