Oh, virtual, new,... modifiers in c# have different rules....so what is the best way or best-practices for learning OOP rules and use them easily...?

Question

I found C# very interesting...but unfortunately (or fortunately ! ) it has many features to implement OOP rules....they have different machanisms and make me sometimes confused....

so what is the best way or best-practices for learning OOP rules and use them easily...?

Answer 1

Your best bet is to learn about OOP principles (encapsulation, inheritance and polymorphism) from a fundamental source. And then worry about particular language implementations later. Once you really understand the fundamental concepts, the language specifics become easy to learn, apply and master.

Answer 2

The best way to learn is to keep things simple and practice (program) a lot. Regarding virtual/new/override, there are three main cases:

1. virtual + override Use virtual in the base class and override in the derived class as in

   class BaseClass
   {
   public void virtual Test(){...}
   }
   class DerivedClass: BaseClass
   {
   public void override Test(){...}
   }

2. abstract + override This is a variant of the previous case where the base member does not define a body

   abstract class BaseClass
   {
   public void abstract Test(){...}
   }
   class DerivedClass: BaseClass
   {
   public void override Test(){...}
   }

3. No modifier This is useful when you don't plan on overriding a method

   class BaseClass
   {
   public void Test(){...}
   }
   class DerivedClass: BaseClass
   {
   public void OtherMethod(){...}
   }

In the this case, there would be a warning if "OtherMethod" was named "Test". Indeed, it would clash with the base method. You can get rid of the warning by adding a "new" modifier as in

abstract class BaseClass  
{  
    public void Test(){...}  
}  
class DerivedClass: BaseClass  
{  
    public new void Test(){...}  
}

However, I would recommend avoiding the "new" modifier if possible since it is somewhat confusing.