Property vs Variable?

That Asian Guy

I've been using properties for quite some time, and it was until today that a question came to me: what's the difference between using a property and a variable? I know properties are better practice, but still... just wondering :).

public int Number
{
get
{
return this.number;
}
set
{
this.number = value;
}
}

vs

public int number = 0;

PIEBALDconsult

You generally have more control over a property, but if you don't need that control then it's just overhead. And have you looked at automatic properties (or whatever they're called)?

That Asian Guy

No, whats that :S?

DaveyM69

There are many reasons - a couple to get you started... 1. Using a property enables you to do validation etc within the object that holds the variable in the getter and setter methods. Imagine if the number variable should be restricted to a certain range under certain situations. If you expose the variable directly you have no control over what goes into it - other than the data type. With a property you can test the value parameter, and raise an exception or set the variable to a different value etc. 2. Properties do not have to refer to an actual variable. e.g.

private int number1;
private int number2;

public int Sum
{
get { return number1 + number2; }
}

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)

That Asian Guy

I see... thanks.

DaveyM69

If you don't 'need' the private variable yourself but are just using it to hold a property's value with no validation then you can do this and the compiler takes care of it all for you. Personally I never use them as I like to be in control of what's happening.

// no need for private int number;
public int Number { get; set; }

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)

PIEBALDconsult

Auto-Implemented Properties

That Asian Guy

What would be the initial value of the property?

DaveyM69

Whatever the intial value of the data type - 0 in the case of an int. All value types have an initial value. Reference types will be null (I believe - I haven't checked) as no instance has yet been created.

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)

Mycroft Holmes

I like these, simple in the above style and can easily be expanded to a normal property if required.

Never underestimate the power of human stupidity RAH

Mark Churchill

A property can be an interface member, whereas a variable can't be. This means changing the definition of a class to add/remove a property is a breaking change. Generally speaking if "Number" is part of the publically available API, then you want to expose it as a property. A variable can be passed by reference (ref/out), a property can't be. A variable has only one access modifier, a property can have a different modifier on get/set. In terms of overhead, the effort of implementation is quite small if you use automatic properties. int Foo { get;set; }. In terms of performance the simple accessor will usually be inlined by JIT, making the performance identical (except on forms - they inherit MarshalByRef). Also as a property is effectively a stub of metadata pointing to getter and setter methods, they can benefit from things like declarative security, etc.

Mark Churchill Director, Dunn & Churchill Pty Ltd Free Download: Diamond Binding: The simple, powerful, reliable, and effective data layer toolkit for Visual Studio.
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DaveyM69

For future extensibility they are useful I suppose - but I've found I nearly always need more control so I do it the 'old fashioned' way! Also, not being able to have true read only properties this way (you have to have a set; - although it can have a private accessor) is a pain.

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)

Mycroft Holmes

I use properties a LOT, I have a class for each table in my BLL and a property for each field in the table (all auto generated) so nearly all of these can be serviced by the auto property. Expanding an auto to a full property is really simple and can be done at any time.

Never underestimate the power of human stupidity RAH

J4amieC

you know you can do this: public int MyInt{get; **private** set; }

DaveyM69

Yeah - in my post...

DaveyM69 wrote:

although it can have a private accessor

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)