What's so special about properties?

Question

I have the basics down with properties, but I don't see a real use for them. Doesn't it just return the value of an equation? I mean there is no point in using a property if you could just write down a simple equation for it.

For example:

int currentValue;

public int CurrentValue
{
    get { return currentValue; }
    set { currentValue = value; }
}

Is the same thing as just:

currentValue;

Another example:

    int currentValue;

public int CurrentValue
{
    get { return currentValue * 5; }
    set { currentValue = value; }
}

Is the same thing as:

currentValue = currentValue * 5;

I am not sure I am following you or you don't have the basics down :). — nphx, Feb 20 '14 at 18:27
Do you mean "Isn't it just the same as exposing the field?" the answer is no, for various reasons. See http://csharpindepth.com/Articles/Chapter8/PropertiesMatter.aspx — Jon Skeet, Feb 20 '14 at 18:30
+1 For `"..properties, but I don't see a real use for them."` — gleng, Feb 20 '14 at 18:30
Properties are MUCH easier to work with when using reflection. — Scottie, Feb 20 '14 at 18:32
@JerkeyTurkey sorry, you have just been Skeet'd. [Properties Matter](http://csharpindepth.com/Articles/Chapter8/PropertiesMatter.aspx), by Jon Skeet. — Federico Berasategui, Feb 20 '14 at 18:33
Another thing that's really special about properties: java doesn't have them. They're one of the thousands of reasons why C# is better than java. — Federico Berasategui, Feb 20 '14 at 18:35
possible duplicate of [Why we need Properties in C#](http://stackoverflow.com/questions/1523548/why-we-need-properties-in-c-sharp) — nawfal, Jul 17 '14 at 20:20

score 4 · Accepted Answer · edited May 23 '17 at 10:31

In your first example, Public Fields versus Automatic Properties is a good answer. Basically, you should use always properties instead of fields for non-private things. This lets you do things like modify the code later without breaking things, and make a private set. Properties can also do things like notify code when they're changed or provide default or calculated values easily. And you can use auto-properties to cut down on extraneous code:

public int CurrentValue { get; set; }

Your second example is not a good use of properties, since it breaks the assumptions of how properties work. E.g. if I set the property to 3 and no exception is thrown, I'd expect it to be 3 when I get it, not 15. currentValue = currentValue * 5;, which could make sense working with a field, property, or local variable, makes the value 5 times larger. Maybe you meant something like this:

int currentBackingValue;

public int CurrentValue
{
    get { return currentBackingValue * 5; }
}

Without a set, this can work nicely, and without breaking any conventions and assumptions: CurrentValue is calculated based on currentBackingValue.

(as an aside, you should note that the getters and setters of a property are, in fact, methods, just used with a field-like syntax to replace something like Java's getX/setX standard)

score 1 · Answer 2 · answered Feb 20 '14 at 18:36

Getters and setters properties are handy if you want to add some extra functionality to your code, centralizing your function so you can change it only in one place. You almost never know when you're going to have to change something, but you can prepare.

This, along with the concepts of encapsulation and information hiding, are basic OOP concepts but very important...

V E R Y I M P O R T A N T

Don't underestimate this tremendous power D:

Its so... powerful...

score 0 · Answer 3 · answered Feb 20 '14 at 18:48

Properties are also used in a number of other .NET technologies, WPF doesn't work without them (with a PropertyChanged event invoke in the setter) and WCF uses them extensively in data contracts.

Especially relating to WPF, the power of properties is that both the "get" and "set" fields are functions and so can do lots of things besides just returning or setting the backing private member. This comes in handy more times than you may think.

Example property (for WPF)

public String UIDisplayedString
{
   get { return _member; }
   set 
   { 
      _member = value;
      PropertyChanged(new PropertyChangedEventArgs("UIDisplayedString"));
   }

What's so special about properties?

3 Answers3