Easiest way to make C# not instantiate a class unless inherit?

Question

What is the easiest way to make C# not instantiate a class unless inherit?

Sounds weird but i dont want to explain the why. I have a base class and two class that inherit it. I want to use the derived class only and not the base. The derive class does not have any extra functions. Whats the easiest way to NOT allow me to write new BaseClass(); so i dont accidentally use it? I do have functions that operate on the base class and not the derived.

Answer 1

Make the class an abstract base class.

abstract class Person {

}

class Programmer : Person {

}

var person = new Person();          // compile time error
var programmer = new Programmer();  // ok

Answer 2

Can the base class be Abstract? That would do it.

Answer 3

Set the class to abstract:

public abstract BaseClass
{



}

http://msdn.microsoft.com/en-us/library/sf985hc5.aspx

Answer 4

public abstract class BaseClass {
...
}

Answer 5

instead of the normal:

"public Class MyClass"

make it

"public abstract Class MyClass"

Answer 6

Make the constructor of BaseClass protected:

public class BaseClass {

   protected BaseClass()
   {
      // DO SOMETHING
   }

}


public class Derived : BaseClass {

   public Derived() {}
}

Answer 7

You make an abstraction with the keyword Abstract.

If you type abstract into a google definition it will tell you that it means "part of" or "not completetly defined" which means exactly what you are looking for.

You cannot create what you do not have meaning that you need to have a complete structure before you can create it, and an abstract class is not complete untill it's inherited!

It's the fundamentals of Object Oriented Programming. Which might bring you to something called Polymorphism which let's you do other very interesting stuff!

Answer 8

The way you describe your need, making your class abstract is the way to go. It will stop you from instantiating the base class and will allow you to call the functions on it. This will also allow you to mark functions and properties as abstract and force the inherited classes to implement them.

If you had no need to share code, an interface would be a nice option. It allows you to implement it in a way very similar to an abstarct class and casting your implementations into it.

Hope this adds some value.