7.10.08

Property in C#:

Property ? it is a special method that can return a current object?s state or set it. Simple syntax of properties can see in the following example:
public int Old
{
get {return m_old;}
set {m_old = value;}
}
public string Name
{
get {return m_name;}
}
Here are two types of properties. A first one can set or get field of class named m_old, and the second is read only. That?s mean it can only get current object?s state.
The significance of these properties is its usability. These properties need not be called with any function names like objectname.get or objectname.set etc., But they can be directly assigned the values or retrieve the values.
Static Properties
C# also supports static properties, which belongs to the class rather than to the objects of the class. All the rules applicable to a static member are applicable to static properties also.
The following program shows a class with a static property.
using System;
class MyClass
{
private static int x;
public static int X
{
get{return x;}
set{x = value;}
}
}
class MyClient
{
public static void Main()
{
MyClass.X = 10;
int xVal = MyClass.X;
Console.WriteLine(xVal);//Displays 10
}
}
Remember that set/get accessor of static property can access only other static members of the class. Also static properties are invoking by using the class name.
Properties & Inheritance
The properties of a Base class can be inherited to a Derived class.
using System;
class Base
{
public int X
{
get
{
Console.Write("Base GET");
return 10;
}
set
{Console.Write("Base SET");}
}
}
class Derived : Base{}
class MyClient
{
public static void Main()
{
Derived d1 = new Derived();
d1.X = 10;
Console.WriteLine(d1.X);//Displays 'Base SET Base GET 10'
}
}
The above program is very straightforward. The inheritance of properties is just like inheritance any other member.
Properties & Polymorphism
A Base class property can be polymorphicaly overridden in a Derived class. But remember that the modifiers like virtual, override etc are using at property level, not at accessor level.
using System;
class Base
{
public virtual int X
{
get
{
Console.Write("Base GET");
return 10;
}
set
{
Console.Write("Base SET");
}
}
}
class Derived : Base
{
public override int X
{
get
{
Console.Write("Derived GET");
return 10;
}
set
{
Console.Write("Derived SET");
}
}
}
class MyClient
{
public static void Main()
{
Base b1 = new Derived();
b1.X = 10;
Console.WriteLine(b1.X);//Displays 'Derived SET Derived GET 10'
}
}
Abstract Properties
A property inside a class can be declared as abstract by using the keyword abstract. Remember that an abstract property in a class carries no code at all. The get/set accessors are simply represented with a semicolon. In the derived class we must implement both set and get assessors.
If the abstract class contains only set accessor, we can implement only set in the derived class.
The following program shows an abstract property in action.
using System;
abstract class Abstract
{
public abstract int X
{
get;
set;
}
}
class Concrete : Abstract
{
public override int X
{
get
{
Console.Write(" GET");
return 10;
}
set
{
Console.Write(" SET");
}
}
}
class MyClient
{
public static void Main()
{
Concrete c1 = new Concrete();
c1.X = 10;
Console.WriteLine(c1.X);//Displays 'SET GET 10'
}
}
The properties are an important features added in language level inside C#. They are very useful in GUI programming. Remember that the compiler actually generates the appropriate getter and setter methods when it parses the C# property syntax.

No comments: