无法注册数据服务Prism Xamarin表单

我正在尝试注册我的服务,以便将参数发送到下一个ViewModel。

这是我的App.Xaml.cs

protected override void RegisterTypes(IContainerRegistry containerRegistry)
    {

        containerRegistry.RegisterForNavigation<NavigationPage>();
        containerRegistry.RegisterForNavigation<View.MainPage, MainPageViewModel>();
        containerRegistry.Register<IService, Service>();
    }

public interface IService
{
    Task<List<TodoItem>> DataAsync();
}

获取数据的我的服务类:

public class Service
{

public List<TodoItem> TodoList { get; private set; }
HttpClient client;

    Service()
    {
        client = new HttpClient();
        client.MaxResponseContentBufferSize = 256000;
    }

        public async Task<List<TodoItem>> DataAsync()
        {

            TodoList = new List<TodoItem>();


            var uri = new Uri(string.Format(Constants.RestUrl, string.Empty));

            try
            {
                var response = await client.GetAsync(uri);
                if (response.IsSuccessStatusCode)
                {
                    var content = await response.Content.ReadAsStringAsync();
                    TodoList = JsonConvert.DeserializeObject<List<TodoItem>>(content);
                    Debug.WriteLine(content);
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine(@"ERROR {0}", ex.Message);
            }

            return TodoList;
        }
    }

我从这行im App.Xaml.cs获取错误:

containerRegistry.Register<IService, Service>();

错误消息: