Object Oriented Programming with C# -some tips

• Avoid default constructors:

  Few objects need to be created without being initialized initialize objects during construction if initialization parameters are known.

  Consider the following code

  MyObject m=new MyObject(); m.x=2; m.y=4;

  versus

  MyObject m=new MyObject(2,4);

  The first method of creating MyObject results in twice as many lines of IL code as the second and is roughly twice slower.

• Avoid excessive inheritance:
  Every time you construct a child class its base class is constructed first.
  When the child class goes out of scope it is destructed
  followed by the base class destruction. Excessive inheritance results in construction/destruction overhead and can lead to dependency of parent classes on its children.

• Do not call virtual functions from a constructor:
  In C# we destinguish between compile time definitions and run time initialization. A a=new B() defines an instance of A initialized through its subclass B. Even though A is initialized through its subclass B, it displays all properties of A an no properties of B. Unfortunately, by calling virtual functions in base class constructor, you can make it behave like B.

  class A {   public int x1=2;   public A()   {     DoIt();   }   public virtual void DoIt()   {     Console.WriteLine("Base");   } }

   

  class B:A {   private bool x;   public int x2=3;   public B()   {   }   public override void DoIt()   {     Console.WriteLine("Child");   }   static void Main()   {     A a=new B(true);//results in Child being printed out   } }

• Do not shadow
  
  Shadowing prevents natural flowing up and down inheritance hierarchy and can result in unexpected behavior.

  class A {   public void fun()   {     Console.WriteLine("Base");   } } class B:A {   public void fun()   {     Console.WriteLine("Child");   } } A a=new B(); //What will a.fun() do ?