best way or best-practices for learning OOP rules

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....

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...?

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

Answer 1

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.

Answer 2

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.