base
suggest changeThe base
keyword is used to access members from a base class. It is commonly used to call base implementations of virtual methods, or to specify which base constructor should be called.
Choosing a constructor
public class Child : SomeBaseClass {
public Child() : base("some string for the base class")
{
}
}
public class SomeBaseClass {
public SomeBaseClass()
{
// new Child() will not call this constructor, as it does not have a parameter
}
public SomeBaseClass(string message)
{
// new Child() will use this base constructor because of the specified parameter in Child's constructor
Console.WriteLine(message);
}
}
Calling base implementation of virtual method
public override void SomeVirtualMethod() {
// Do something, then call base implementation
base.SomeVirtualMethod();
}
It is possible to use the base keyword to call a base implementation from any method. This ties the method call directly to the base implementation, which means that even if new child classes override a virtual method, the base implementation will still be called so this needs to be used with caution.
public class Parent
{
public virtual int VirtualMethod()
{
return 1;
}
}
public class Child : Parent
{
public override int VirtualMethod() {
return 11;
}
public int NormalMethod()
{
return base.VirtualMethod();
}
public void CallMethods()
{
Assert.AreEqual(11, VirtualMethod());
Assert.AreEqual(1, NormalMethod());
Assert.AreEqual(1, base.VirtualMethod());
}
}
public class GrandChild : Child
{
public override int VirtualMethod()
{
return 21;
}
public void CallAgain()
{
Assert.AreEqual(21, VirtualMethod());
Assert.AreEqual(11, base.VirtualMethod());
// Notice that the call to NormalMethod below still returns the value
// from the extreme base class even though the method has been overridden
// in the child class.
Assert.AreEqual(1, NormalMethod());
}
}
Found a mistake? Have a question or improvement idea?
Let me know.
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