C#: Specifying behavior for the “default” keyword when using generics

public class GenericClass<T> where T : new() {
    //class definition

    private void SomeMethod() {
        T myT = new T();
        //work with myT
    }
}

public class foo
{
    public string bar = "abc";
}

public class Container<T>
{
    T MaybeFoo = default;
}

a = new Container<foo>();

// a.MaybeFoo is null;

public class foo
{
    public string bar = "abc";
}

public class Container<T> where T : new()
{
    T MaybeFoo = new T();
}

a = new Container<foo>();

Console.WriteLine( ((Foo)a.MaybeFoo).bar )  // prints "abc"