Model with constructor vs. Model without constructor ASP.NET MVC

Question

I am working on a project in ASP.NET MVC. I've been looking for some learning resources regarding the subject and I've come across a scenario which I'm searching for clarification. Suppose:

public class Foo
{
    public int Id { get; set; }
    public string FooName { get; set; }
    public virtual Bar Bar { get; set; }
}

and

public class Bar
{
    public Bar()
    {
        this.Foos = new List<Foo>;
    }

    public int Id { get; set; }
    public string BarDesc { get; set; }
    public virtual List<Foo> Foos { get; set; }
}

I mean, in what way does it differ from that of a model Bar with no constructor? Please disregard any errors in the properties (if there any) or possible relationship within entities, since I just want clarification about having a constructor inside a model. Thanks!

Answer 1

With the constructor you've shown, Bar.Foos will be an empty List of type Foo.

Without the constructor, Bar.Foos will be null (unless you initialize it elsewhere).

It's the same difference you'd see between these two lines:

List<SomeType> test1 = null;
List<SomeType> test2 = new List<SomeType>();

Assuming you're using C# 6, another way of initializing it without a constructor is:

public class Bar
{
    public int Id { get; set; }
    public string BarDesc { get; set; }
    public virtual List<Foo> Foos { get; set; } = new List<Foo>();
}

Which of the 3 techniques you choose will be up to you, based on whether you always want the property to be initialized or not, if you have multiple constructors, which you think looks better, how you feel about null collection references vs empty collections etc.