base (C# Reference)

The base keyword is used to access members of the base class from within a derived class:

• Call a method on the base class that has been overridden by another method.

• Specify which base-class constructor should be called when creating instances of the derived class.

A base class access is permitted only in a constructor, an instance method, or an instance property accessor.

It is an error to use the base keyword from within a static method.

The base class that is accessed is the base class specified in the class declaration. For example, if you specify class ClassB : ClassA, the members of ClassA are accessed from ClassB, regardless of the base class of ClassA.

Example

In this example, both the base class, Person, and the derived class, Employee, have a method named Getinfo. By using the base keyword, it is possible to call the Getinfo method on the base class, from within the derived class.

 public class Person
 {
 protected string ssn = "444-55-6666";
 protected string name = "John L. Malgraine";
 public virtual void GetInfo()
 {
 Console.WriteLine("Name: {0}", name);
 Console.WriteLine("SSN: {0}", ssn);
 }
 }
 class Employee : Person
 {
 public string id = "ABC567EFG";
 public override void GetInfo()
 {
 // Calling the base class GetInfo method:
 base.GetInfo();
 Console.WriteLine("Employee ID: {0}", id);
 }
 }
 class TestClass
 {
 static void Main()
 {
 Employee E = new Employee();
 E.GetInfo();
 }
 }
 /*
 Output
 Name: John L. Malgraine
 SSN: 444-55-6666
 Employee ID: ABC567EFG
 */

For additional examples, see new, virtual, and override.

This example shows how to specify the base-class constructor called when creating instances of a derived class.

public class BaseClass
{
 int num;
 public BaseClass()
 {
 Console.WriteLine("in BaseClass()");
 }
 public BaseClass(int i)
 {
 num = i;
 Console.WriteLine("in BaseClass(int i)");
 }
 public int GetNum()
 {
 return num;
 }
}
public class DerivedClass : BaseClass
{
 // This constructor will call BaseClass.BaseClass()
 public DerivedClass() : base()
 {
 }
 // This constructor will call BaseClass.BaseClass(int i)
 public DerivedClass(int i) : base(i)
 {
 }
 static void Main()
 {
 DerivedClass md = new DerivedClass();
 DerivedClass md1 = new DerivedClass(1);
 }
}
/*
Output:
in BaseClass()
in BaseClass(int i)
*/

C# Language Specification

For more information, see the C# Language Specification. The language specification is the definitive source for C# syntax and usage.

See Also

Reference

C# Keywords

this (C# Reference)

Concepts

C# Programming Guide

Other Resources

C# Reference