Properties

v Properties

→   Another type of class member is the property. As a general rule, a property combines a field with the methods that access it.

→   You will often want to create a field that is available to users of an object, but you want to maintain control over the operations allowed on that field.

→    For instance, you might want to limit the range of values that can be assigned to that field. While it is possible to accomplish this goal through the use of a private variable along with methods to access its value, a property offers a better, more streamlined approach.

→   Properties are similar to indexers. A property consists of a name along with get and set accessors. The accessors are used to get and set the value of a variable.

→   The key benefit of a property is that its name can be used in expressions and assignments like a normal variable, but in actuality the get and set accessors are automatically invoked. This is similar to the way that an indexer’s get and set accessors are automatically used.

→   The general form of a property is shown here:

type name

{

get

{

// get accessor code

}

set

{

// set accessor code

}

}

→   Here, type specifies the type of the property, such as int, and name is the name of the property. Once the property has been defined, any use of name results in a call to its appropriate accessor. The set accessor automatically receives a parameter called value that contains the value being assigned to the property.

    

→   Here is a simple example that defines a property.

using System;

class test

{

    private int no;

    public int pno

    {

        get

        {

          return no;

        }

        set

        {

            no = value;

        }

    }

}

class Program

{

    static void Main(string[] args)

    {

        test t=new test();

        t.pno=13;

        int temp=t.pno;

        Console.WriteLine("No. is = {0}",temp);

        Console.ReadLine();

    }

}

→   Output

No. is = 13

Þ   Property Restrictions

→   Properties have some important restrictions. First, because a property does not define a storage location, it cannot be passed as a ref or out parameter to a method.

→   You cannot overload a property. (You can have two different properties that both access the same variable, but this would be unusual.)

→   A property should not alter the state of the underlying variable when the get accessor is called. Although this rule is not enforced by the compiler, violating it is semantically wrong. A get operation should be nonintrusive.