What is the difference between public int i and public int i {get; set;} (what is the difference between automatic property and a public member?) [duplicate]

Question

Possible Duplicates:
c#: why have empty get set properties instead of using a public member variable?
C#: Public Fields versus Automatic Properties

I am using "automatic" properties in my code, and I wonder what is the actual difference between this code:

public class foo{
    public int i;
}

and

public class foo{
    public int i {get; set;}
}

I know there is a difference, as sine 3rd parties that I've used missed the public members but found them once adding the {get; set;}.

AS there is no private field behind that, what is going behind the scene ?

Answer 1

A private field gets generated by the compiler when using automatic properties.

When you declare a property as shown in the following example, the compiler creates a private, anonymous backing field that can only be accessed through the property's get and set accessors.

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In regards to the difference between the two examples - the first one exposes the field directly for manipulation. This is considered bad practice (think information hiding, loss of encapsulation).

With the second example, you must use the getter and setter and you can add any kind of validation and other logic around these actions.

See this blog post:

If I have a field with no special behavior, should I write a "just in case" property (with trivial get/set), or should I expose a public field?

The reason that the library design guidelines suggest you write a property here is that it is important that libraries be easily versioned. If you put a property in there ahead of time, you can change the property implementation without requiring users to recompile their code.