Why can't I inject a dependancy into a ContentPage?

Question

Please see the code below:

public partial class MyContentPage : ContentPage
    {

        public CreditCardView()
        {
            InitializeComponent();
        }
}

It works as expected. Now say I want to inject a dependancy:

public partial class MyContentPage : ContentPage
    {
        private readonly IMyService _myService;

        public CreditCardView(IMyService myService)
        {
            InitializeComponent();
            _myService=myService;
        }
}

With the second excerpt of code I see a compilation error: "The given key was not present in the dictionary". What is the problem? I have registered the dependancy.