Abstract Data Type in C#

• Access qualifiers:
  • public, protected, private as in Java
  • internal and protected internal - visible to all classes in the assembly
• Separation of abstraction from encapsulation: can use partial class definition:

  public partial class Student
  {
      public void Study()
      {
      }
  }
  
  public partial class Student
  {
      public void Socialize()
      {
      }
  }
  

• Types of functions:
  • Default constructor provided to initialize all data members with default values
    • Default constructor initializes any data member not initialized by programmer-defined constructor
  • Destructor unnecessary
  • Programmers can use properties to provide accessors

         public class Time
         {
            public int hourProperty   // property for hour data member
            {
               get { return hour; }
               set { hour = ( value < 24 ? value : 0; }  // value is implicit variable
            }
     
            private int hour;  // The actual data member
         }
    
         // In client
         Time now = new Time();
         int thisHour = now.hourProperty;   // No explicit function call involved
         now.hourProperty = thisHour + 2;
         

    • No explicit function call needed in client
    • Access to data member only through property
• Struct: Alternative to Class
  • Lightweight class - does not support inheritance
  • Variable is value type, not reference types like objects
  • Variable allocated on stack, not heap
  • Passed by value to functions
  • All primitive types are structs
• Client:
  • All objects allocated from the heap
• Parameterized ADT:
  • Pre-2005: Collection classes ArrayList, Stack, Queue - had same problems as Java pre-5.0
  • Post 2005:
    • ArrayList, Stack, Queue, Dictionary - similar design to Java
    • Only a programmer-specified type can be added to the container
    • No need to cast when removing element from the container
    • Programmer-defined generic collection class can be defined to allow elements to be accessed through subscripts