// Fig. 11.4: Employee.cs
// Employee abstract base class.
public abstract class Employee
{
   private string firstName;
   private string lastName;
   private string socialSecurityNumber;

   // three-parameter constructor
   public Employee( string first, string last, string ssn )
   {
      firstName = first;
      lastName = last;
      socialSecurityNumber = ssn;
   } // end three-parameter Employee constructor

   // read-only property that gets employee's first name
   public string FirstName
   {
      get
      {
         return firstName;
      } // end get
   } // end property FirstName

   // read-only property that gets employee's last name
   public string LastName
   {
      get
      {
         return lastName;
      } // end get
   } // end property LastName

   // read-only property that gets employee's social security number
   public string SocialSecurityNumber
   {
      get
      {
         return socialSecurityNumber;
      } // end get
   } // end property SocialSecurityNumber

   // return string representation of Employee object, using properties
   public override string ToString()
   {
      return string.Format( "{0} {1}\nsocial security number: {2}",
         FirstName, LastName, SocialSecurityNumber );
   } // end method ToString

   // abstract method overridden by derived classes
   public abstract decimal Earnings(); // no implementation here
} // end abstract class Employee


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