Question

Ok, so basically I need to create a generic method which takes a list of frontend objects, retrieves the wrapped data object of each frontend object and returns a list of data objects.

I have written this method inside a singleton class.

public IEnumerable<T> GetDataItemsFromFrontend<T>(IEnumerable<T> frontendItems)
    {
        List<T> dataItems = new List<T>();
        foreach(T frontendItem in frontendItems)
            {
                dataItems.Add(T.GetDataItem());
            }
        return dataItems;
    }

Quite naturally, T.GetUser() does not exist. To give you a better idea of what I intend to do:

I have an entity object called User (generated by the Entity-Model Framework). To add functionality to User, I created a wrapper object called ClassFrontend where class is replaced by the entity title in question (for example, UserFrontend, RoleFrontend, etc).

I called the entity object inside the frontend class Data.

Now I would like to have a Generic method, which I give it a list of frontend items, and it gives me back a list of entity objects – naturally the list would be all of the same type: example all of UserFrontend, or all of RoleFrontend, etc.

Thanks.

Answer 1

I would make the FrontEnd objects implement an interface like below:

public interface IFrontEndEntity<TEntity>
{
    TEntity GetEntity();
}
public static class FrontEndExtensions
{
    public static IEnumerable<TEntity> GetEntities<TEntity>(this IEnumerable<IFrontEndEntity<TEntity>> frontEndItems)
    {
        return frontEndItems.Select(a => a.GetEntity());
    }
}
public class Dog
{
}
public class DogFrontEnd : IFrontEndEntity<Dog>
{
    public Dog Entity { get; set; }
    public Dog GetEntity()
    {
        return Entity;
    }
}
public class Main
{
    public void Run()
    {
        IEnumerable<DogFrontEnd> dogFronEnds = new List<DogFrontEnd>();
        IEnumerable<Dog> dogs = dogFronEnds.GetEntities();
    }
}