Correct use of C# properties

Question

private List<Date> _dates;

public List<Date> Dates
{
    get { return _dates; }
    set { _dates = value; }
}

OR

public List<Date> Dates
{
    get;        
    set;    
}

I have always used the former, is that incorrect or bad practice? It never occurred to me that I could just use the second option. I do like having my encapsulated variables to begin with an underscore so I can distinguish them from method parameters. And I've just always done it that way.

Is it possible that using the first option would result in an extra List<Date> object being instantiated and then the whole of _dates being replaced with value, or is it more intelligent than that?

Also, which is the most prominent in industry or is it totally subjective?

Answer 1

Use the former if you need to add some kind of logic to your getter/setters.

Use the latter otherwise. It makes things much cleaner. You can also achieve read-only properties using auto properties:

public List<Date> Dates { get; private set; }

Or, if you don't want people to add any items to the list through the property you can resort to the former syntax:

private List<Date> _dates = new List<Date>();
private ReadOnlyCollection<Date> _readOnlyDates =
    new ReadOnlyCollection<Date>(_dates);

public ReadOnlyCollection<Date> Dates
{
    get { return _readOnlyDates; }
}