• Introduction
• Struct types
• Primitive types
• Enumeration types

• The value types are the struct types, primitive types and enumeration types.

• The declaration of a struct type is similar to that of a class type.
• For example, it can declare fields, constructors and methods.
• However, the big difference is: a variable that is of some class type points to an object of that class whereas a variable that is of some struct type stores the value itself.
• So assignment between two structs causes copying of a struct value to take place rather than making a variable point to the same object as some other variable.
• The other big difference is that a struct variable is stored on the stack (or is inline) whereas a class object is stored on the heap.

Here is an example of a struct type coded in C#:

public struct SPoint
{
    private int iX;
    private int iY;
    public SPoint(int pX, int pY)
    {
        iX = pX;
        iY = pY;
    }
    public override string ToString()
    {
        return iX + ":" + iY;
    }
}

Here is a method that uses this struct type:

using System;
public class SPointTest
{
    public static void Main()
    {
        SPoint tSPoint = new SPoint(100, 200);
        Console.WriteLine(tSPoint);
        SPoint tAnotherSPoint = tSPoint;
        Console.WriteLine(tAnotherSPoint);
    }
}

• You cannot extend struct types (e.g., to produce NamedSPoint).
• Use structs for lightweight objects.

In C#, each primitive type is just an alias for a struct type.

• C# also has enumeration types.
• Here is an example:

  enum Days : int
  {
      Sunday = 1,
      Monday, Tuesday, Wednesday, Thursday, Friday,
      Saturday
  }
  

• Each enum declaration introduces a new type.