What is the difference between a class and an object in C#?

When you define a class, you define a blueprint for a data type.

Objects are instances of a class. The methods and variables that constitute a class are called members of the class.

To access the class members, you use the dot (.) operator after the object name. The dot operator links the name of an object with the name of a member for example,

Box Box1 = new Box();

Above you can see Box1 is our object. We will use it to access the members −

Box1.height = 7.0;

You can also use it to call member functions −

Box1.getVolume();

The following is an example showing how objects and class work in C# −

Example

 Live Demo

using System;

namespace BoxApplication {
   class Box {
      private double length; // Length of a box
      private double breadth; // Breadth of a box
      private double height; // Height of a box

      public void setLength( double len ) {
         length = len;
      }

      public void setBreadth( double bre ) {
         breadth = bre;
      }

      public void setHeight( double hei ) {
         height = hei;
      }

      public double getVolume() {
         return length * breadth * height;
      }
   }

   class Boxtester {
      static void Main(string[] args) {
         // Creating two objects
         Box Box1 = new Box(); // Declare Box1 of type Box
         Box Box2 = new Box();
         double volume;

         // using objects to call the member functions
         Box1.setLength(6.0);
         Box1.setBreadth(7.0);
         Box1.setHeight(5.0);

         // box 2 specification
         Box2.setLength(12.0);
         Box2.setBreadth(13.0);
         Box2.setHeight(10.0);

         // volume of box 1
         volume = Box1.getVolume();
         Console.WriteLine("Volume of Box1 : {0}" ,volume);

         // volume of box 2
         volume = Box2.getVolume();
         Console.WriteLine("Volume of Box2 : {0}", volume);

         Console.ReadKey();
      }
   }
}

Output

Volume of Box1 : 210
Volume of Box2 : 1560