Inheritance

sealed prevents inheritance from occurring

// The MiniVan class cannot be extended! 
sealed class MiniVan : Car 
{ 
}

Initialize Base Class

// As a general rule, all subclasses should explicitly call an appropriate base class constructor. 
public SalesPerson(string fullName, int age, int empID, 
  float currPay, string ssn, int numbOfSales) 
  : base(fullName, age, empID, currPay, ssn) 
{ 
  // This belongs with us! 
  SalesNumber = numbOfSales; 
} 

Delegation Delegation is simply the act of adding public members to the containing class that make use of the contained object’s functionality

//Declare Employee with BenefitPackage
public partial class Employee 
{ 
  // Contain a BenefitPackage object. 
  protected BenefitPackage empBenefits = new BenefitPackage(); 
 
  // Expose certain benefit behaviors of object. 
  public double GetBenefitCost() 
{ return empBenefits.ComputePayDeduction(); } 
 
  // Expose object through a custom property. 
  public BenefitPackage Benefits 
  { 
    get { return empBenefits; } 
    set { empBenefits = value; } 
  } 
... 
}

Using Delegation class

static void Main(string[] args) 
{ 
  Console.WriteLine("***** The Employee Class Hierarchy *****\n"); 
  Manager chucky = new Manager("Chucky", 50, 92, 100000, "333-23-2322", 9000); 
  double cost = chucky.GetBenefitCost(); 
  Console.ReadLine(); 
} 

Nested Class

• Nested types allow you to gain complete control over the access level of the inner type, as they may be declared privately (recall that non-nested classes cannot be declared using the private keyword).
• Because a nested type is a member of the containing class, it can access private members of the containing class
• Oftentimes, a nested type is only useful as a helper for the outer class, and is not intended for use by the outside world

Example
public class OuterClass 
{ 
  // A public nested type can be used by anybody. 
  public class PublicInnerClass {} 
 
  // A private nested type can only be used by members of the containing class. 
  private class PrivateInnerClass {} 
} 

Scope of inner class
static void Main(string[] args) 
{ 
  // Create and use the public inner class. OK! 
  OuterClass.PublicInnerClass inner; 
  inner = new OuterClass.PublicInnerClass(); 
 
  // Compiler Error! Cannot access the private class. 
  OuterClass.PrivateInnerClass inner2; 
  inner2 = new OuterClass.PrivateInnerClass(); 
}

nested class
partial class Employee  ***Partial keyword***
{ 
  public class BenefitPackage  ***nested class***
  { 
    // Assume we have other members that represent 
    // dental/health benefits, and so on. 
    public double ComputePayDeduction() 
    { 
      return 125.0; 
    } 
  } 
... 
}