Question

Many times I have seen code where they write a Class like this:

public class Detail
{
    public Detail()
    {
        this.ColumnCtrl = new List<UserControl>();
    }
    public List<UserControl> ColumnCtrl { get; set; }
}

But if I only write the following – it works very fine also:

public class Detail
{
    public List<UserControl> ColumnCtrl { get; set; }
}

Is there any reason to write my get-set Classes like in the first example?

Answer 1

Your first example initializes the ColumnCtrl property to a value when the Detail class is constructed, where your second one will be left null. If it isn’t initialized elsewhere you should expect NullReferenceExceptions.

As long as you initialize the ColumnCtrl property explicitly before use when using your second example, they are exactly the same thing.

Detail newDetail = new Detail();
newDetail.ColumnCtrl = new List<UserControl>();
newDetail.ColumnCtrl.Add(new UserControl());

An alternative (though slightly more verbose) would be to lazily instantiate the ColumnCtrl property to eliminate the overhead of instantiating it when Detail is constructed:

public class Detail
{
    public Detail()
    {
        this.ColumnCtrl = new List<UserControl>();
    }
    private List<UserControl> columnCtrl = null;
    public List<UserControl> ColumnCtrl
    {
        get 
        {
            // Missing appropriate locking mechanisms for brevity
            if (columnCtrl == null)
                columnCtrl = new List<UserControl>();

            return columnCtrl;
        }
        // The set is not absolutely necessary if you never need to set it
        // from outside of Details but if you do...
        set
        {
            columnCtrl = value;
        }
    }
}