Web服务的泛型方法和接口在C＃？

Question

In a Windows Phone application, i consume multiple webservices from different providers. In order to bind the datas in the xaml, i have a class to rule them all. Let's say :

public class Event
{
  public string Id { get;set;}
  public string Title { get;set;}
  public string Latitude { get;set;}
  public string Longitude { get;set;}
}

When a provider has one webservice, i use a method like :

private List<Event> MigrateCompanyEventToEvent(DataServiceCollection<CompanyEvent> collection)
{
   var listEvents = new List<Event>();
   foreach(var item in collection)
   {
      var ev = new Event();
      ev.Id = item.itemId.ToString(); //typeof Guid();
      ev.Title = item.companyEventTitle;
      if(item.latitude != null) { ev.Latitude = item.latitude.ToString(); } //typeof double?
      //etc.
      listEvents.Add(ev);
   }
   return listEvents;
}

But... I have a provider with a lot of similar webservices. I don't want to write a method for each one so i looked at generics methods. I think i don't understand something.

I have a webservices named KidEvents, ParentalEvents, SingleEvents... all with the same definition. So, I wrote an Interface :

public interface IdataEvents<T>
{
     Guid entity_id {get;}
     string nameEvent {get;}
     double? latitude {get;}
     double? longitude {get;}
}

And to proceed I wrote :

private List<Event> MigrateGenericOdataToEvent<T>(DataServiceCollection<T> collection) where T:IdataEvents<T>
{
    var listEvents = new List<Event>();
    foreach(T item in collection)
    {
       var ev = new Event();
       ev.Title = item.nameEvent;
       ev.Id = item.entity_id;
       //etc.
       listEvents.Add(ev);
    }
    return listEvents
}

My problem is, when i use : var SingleEvents = MigrateGenericOdataToEvent(collection); //with collection typeof DataServiceCollection

i get an error :

Le type 'm3.ServiceReferenceData.SingleEvents' ne peut pas être utilisé 
comme paramètre de type 'T' dans le type ou la méthode générique 
'm3.ViewModels.MainViewModel.MigrateGenericOdataToEvent<T>
(System.Data.Services.Client.DataServiceCollection<T)'. 
Il n'y a pas de conversion de référence implicite de 
'm3.ServiceReferenceData.SingleEvents' en 
'm3.ViewModels.IdataEvents<m3.ServiceReferenceData.SingleEvents>'.  

Sorry, it's in french... It means something like :

The type 'm3.ServiceReferenceData.SingleEvents' can not be used as a paramater 
of type 'T' in the type or generic method 
'm3.ViewModels.MainViewModel.MigrateGenericOdataToEvent<T>
(System.Data.Services.Client.DataServiceCollection<T)'. 
There is no implicit conversion reference of 'm3.ServiceReferenceData.SingleEvents' 
in 'm3.ViewModels.IdataEvents<m3.ServiceReferenceData.SingleEvents>'

Is it possible to parse datas from SingleEvents, ParentalEvents, KidEvents (all same data model) to one generic Event ? And how can i do that please ?

Thank you very much

Answer 1

The error you are getting is because of this part of your function definition:

where T:IGenericOdata<T>

(Based on the exception message, I'm assuming that your actual code uses IdataEvents<T> and not IGenericOdata<T> , otherwise the exception doesn't make much sense.)

It is complaining that your data types do not actually implement the interface that you have in your constraint. You've told the compiler that only things that implement the interface are allowed to be used as T , but you are sending in a type that doesn't implement the interface.

If these types are coming from an auto-generated service reference, you can take advantage of the fact that the data types are implemented as partial classes by the reference code generator, and extend them to implement your new interface by simply making another partial class file. Alternatively, you could create a wrapper class around each of the service reference classes and implement your interface there.