freeCodeCamp/guide/english/csharp/class/index.md

title
Class

Class

A class in C# is defined as a reference type. In order to instatiate a variable of with a reference type you must specify the new keyword, else the variable will have the default value of null. See below for an example.

// The value of variableOne is null at this point.
NewClass variableOne;

// Now the value of variableOne will be an instance of the class NewClass
variableOne = new NewClass();

At runtime when the class is created enough memory is allocated onto the heap for that specific instance of the class that the variable holds.

Creating Classes

To create a class in C# we need to use the class keyword followed by a unique identifier.

Like other languages, C# creates a default constructor that accepts no parameters. We can also specify our own constructor if we need to take in special parameters or have custom initlization steps in our constructor.

public class NewClass
{
    NewClass(string name)
    {
        // Initialization steps...
    }
}

A class is a prototype or blueprint from which objects are created. In C#, the class is defined by using the keyword class. A class is used to combine together some methods, properties, fields, events, and delegates into a single unit. A class may contain nested classes too.

Example: Consider the case of Employee Class below:

using System;

namespace CPrograms
{
    class Employee
    {
        private string name;
        private int employeeId;

        public Employee(string name, int employeeId)
        {
            this.name = name;
            this.employeeId = employeeId;
        }
        public void PrintEmployee()
        {
            Console.WriteLine("Employee Name: {0} , Employee ID: {1}", this.name, this.employeeId);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Employee employeeObject = new Employee("John Doe", 420156);
            employeeObject.PrintEmployee();
        }
    }
}

A class can inherit from one base class only. However, it can implement from more than one interface.

More Information

Read more about classes here