base
Visual Studio .NET 2003
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.
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.
// keywords_base.cs
// Accessing base class members
using System;
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 {
public 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.
Example
This example shows how to specify the base-class constructor called when creating instances of a derived class.
// keywords_base2.cs
using System;
public class MyBase
{
int num;
public MyBase()
{
Console.WriteLine("in MyBase()");
}
public MyBase(int i )
{
num = i;
Console.WriteLine("in MyBase(int i)");
}
public int GetNum()
{
return num;
}
}
public class MyDerived: MyBase
{
// This constructor will call MyBase.MyBase()
public MyDerived() : base()
{
}
// This constructor will call MyBase.MyBase(int i)
public MyDerived(int i) : base(i)
{
}
public static void Main()
{
MyDerived md = new MyDerived();
MyDerived md1 = new MyDerived(1);
}
}
Output
in MyBase() in MyBase(int i)
