C# Base Keyword

When you have inheritance between two or more classes. One is base classs (parent class). Another is derived class (child class). You want to access the members such as fields, properties, and methods, within a derived class. In this type of situation you can use base keyword in derived class to access members of base class.

C# Base Class Keyword

Some Important Features of base Keyword

  • Accessing Base Class Constructor:

    When you want to explicitly call a constructor of the base class from within a constructor of the derived class. You can write the code with base keyword before the call of the constructor of the derived call. It will execute the base classs constructor before the execution of the derived class constructor.

    Example

    In below example, we have Fruit (parent class) which have a constructor with name Fruit(string name). We have inherited the Fruit (parent class) with Apple (chile class). We also have a Apple(string name) child class constructor that is inheirted with base class constructor with : base(name) keword.

    // Base class (parent class)

    public class Fruit
    {

    // Base class constructor.

    public Fruit()
    {
    Console.WriteLine("Fruit name is Apple and variety is RedDelicious");
    }
    public Fruit(string name)
    {
    Console.WriteLine("Fruit name is : {0}", name);
    }
    public Fruit(string name, string variety)
    {
    Console.WriteLine("Fruit name is {0} and and variety is {1} ", name, variety);
    }
    public Fruit(string name, string variety, double price)
    {
    Console.WriteLine("Fruit name is {0} and variety is {1} and price is {2}", name, variety, price);
    }
    }

    // Derive class (child class)

    public class Apple: Fruit
    {

    // Derived class constructor.

    public Apple(): base()
    {
    Console.WriteLine("RedDelicious apple has sweet, tart eating taste");
    }
    public Apple(string name): base(name)
    {
    Console.WriteLine("{0} has sweet, tart eating taste", name);
    }
    public Apple(string name, string variety): base(name, variety)
    {
    Console.WriteLine("{0} {1} has sweet, tart eating taste", name, variety);
    }
    public Apple(string name, string variety, double price): base(name,variety,price)
    {
    Console.WriteLine("{0} {1} has sweet, tart eating taste and it's price is {2}$", name, variety, price);
    }
    }

  • Accessing Base Class Members:

    You can use the base keyword to access and call members of the base class, even if those members are hidden or overridden in the derived class. In below example, We have Fruit (parent class) that have Color field. We have inherited child class Apple with Fruit parent class and with base keword we are accessing parent class member (Color) in child Apple class.

    Example

    // Base class (parent class)

    public class Fruit
    {
    public string Color = "Red";
    }

    // Derive class (child class)

    public class Apple: Fruit
    {
    string Color = "Green";

    // Base class field

    Console.WriteLine("Apple color is : {0}", base.Color);

    // Derived class field.

    Console.WriteLine("Apple color is : {0}", Color);
    }

  • base: Example

    using System;
    public class CSharpProgram
    {
    public static void Main(string[] args)
    {

    //Child class instance

    Apple objFruit1 = new Apple();
    Apple objFruit2 = new Apple("Apple");
    Apple objFruit3 = new Apple("Apple", "Honeycrisp");
    Apple objFruit4 = new Apple("Red", "Golden Delicious", 3.16);
    objFruit1.getFruit("Apple");
    }
    }

    // Base class (parent class)

    public class Fruit
    {

    // Base class field.

    public string Color = "Red";

    // Base class constructor.

    public Fruit()
    {
    Console.WriteLine("Fruit name is Apple and variety is RedDelicious");
    }
    public Fruit(string name)
    {
    Console.WriteLine("Fruit name is {0}", name);
    }
    public Fruit(string name, string variety)
    {
    Console.WriteLine("Fruit name is {0} and and variety is {1} ", name, variety);
    }
    public Fruit(string name, string variety, double price)
    {
    Console.WriteLine("Fruit name is {0} and variety is {1} and price is {2}$", name, variety, price);
    }

    // Base class method.

    public virtual void getFruit(string fruitName)
    {

    // Base class method code

    Console.WriteLine("Fruit name is {0} and it's color is {1}", fruitName, Color);
    }
    }

    // Derive class (child class)

    public class Apple: Fruit
    {

    // Derive class constructor.

    public Apple(): base()
    {
    Console.WriteLine("RedDelicious apple has sweet, tart eating taste");
    }
    public Apple(string name): base(name)
    {
    Console.WriteLine("{0} has sweet, tart eating taste", name);
    }
    public Apple(string name, string variety): base(name, variety)
    {
    Console.WriteLine("{0} {1} has sweet, tart eating taste", name, variety);
    }
    public Apple(string name, string variety, double price): base(name,variety,price)
    {
    Console.WriteLine("{0} {1} has sweet, tart eating taste and it's price is {2}$", name, variety, price);
    }

    // Derive class method.

    public override void getFruit(string fruitName)
    {
    base.getFruit("Apple");
    Console.WriteLine("{0} has sweet, tart eating taste and it's color is {1}", fruitName, base.Color);
    }
    }


    Output

    Fruit name is Apple and variety is RedDelicious
    RedDelicious apple has sweet, tart eating taste
    Fruit name is : Apple
    Apple has sweet, tart eating taste
    Fruit name is Apple and and variety is Honeycrisp
    Apple Honeycrisp has sweet, tart eating taste
    Fruit name is Red and variety is Golden Delicious and price is 3.16$
    Red Golden Delicious has sweet, tart eating taste and it's price is 3.16$
    Fruit name is Apple and it's color is Red
    Apple has sweet, tart eating taste and it's color is Red

    Here's a basic breakdown of how Fruit class is working in below exmaple:
    public class Fruit

    Here, Fruit is parent class that is public which mean this class is accessible outside the class.
    public string Color = "Red";

    Here, Fruit class has Color data member which is public that mean it is accessible outside the class and it's data type is string.
    public Fruit()

    {

    Console.WriteLine("Fruit name is Apple and variety is RedDelicious");

    }

    Here, Fruit() is constructor of Fruit class
    public virtual void getFruit(string fruitName)

    {

    // Base class method code

    Console.WriteLine("Fruit name is : {0} and it's color is :{1}", fruitName, Color);

    }

    Here, getFruit(string fruitName) is virtual method that accessible in Fruit parent class.
    Here's a basic breakdown of how Apple subclass is working in below exmaple:
    public class Apple: Fruit

    Here, Apple is child class of Fruit that is inherited with Fruit parent class.
    public Apple() : base()

    {

    // Derived class constructor code

    Console.WriteLine("RedDelicious apple has sweet, tart eating taste");

    }

    Here, Apple() is child class constructor that is inherited with parent class constructor with : base keword. Here base class constructor will call first then child class constructor will call.
    public override void getFruit(string fruitName)

    {

    base.getFruit("Apple");

    Console.WriteLine("{0} has sweet, tart eating taste and it's color is {1}", fruitName, base.Color);

    }

    Here, getFruit(string fruitName) is a method that is overridden in Apple child class from Fruit base class and with base keword we are calling Fruit class method getFruit("Apple");

Summary

You can access the members of base class with derive classs by using base keyword with derived class. When you want to work with members from the base class, even if those members are hidden or overridden in the derived class, You can use base keyword.

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