Question
I've created a generic ObjectSet<T> in my generic repository.
What I would like to get is the name of the EntityKey of ObjectSet<T> so that I can use it in the DataContext.GetObjectByKey.
I've searched around and dug deep, but I can't seem to find this value anywhere in the ObjectSet class.
Accepted Answer
I looked a while ago for a nice way to do this and failed to find one. I generally end up building a GetEntityByKey extension method somewhere and within that, contatenating strings to build Entity Keys for TryGetObjectByKey calls. The general idea for building the entity key goes something like this:
internal class Program
{
private static void Main(string[] args)
{
var dc = new AdventureWorksLT2008Entities();
object c;
dc.TryGetObjectByKey(GetEntityKey(dc.Customers, 23), out c);
var customer = c as Customer;
Console.WriteLine(customer.EmailAddress);
}
private static EntityKey GetEntityKey<T>(ObjectSet<T> objectSet, object keyValue) where T : class
{
var entitySetName = objectSet.Context.DefaultContainerName + "." + objectSet.EntitySet.Name;
var keyPropertyName = objectSet.EntitySet.ElementType.KeyMembers[0].ToString();
var entityKey = new EntityKey(entitySetName, new[] {new EntityKeyMember(keyPropertyName, keyValue)});
return entityKey;
}
}
You may be able to do something similar. This example assumes a single field per EntityKey for simplicity - for multiple value keys you would need to do something slightly more sophisticated with ObjectSet<T>.ElementType.KeyMembers and pass all your keys into the EntityKey constructor.
Popular Answer
Generic:
public class GenericoRepositorio<T> : IGenericoRepositorio<T> where T : class
{
protected readonly ObjectSet<T> ObjetoSet;
protected readonly ModeloContainer Contexto;
public GenericoRepositorio(ModeloContainer contexto)
{
Contexto = contexto;
ObjetoSet = Contexto.CreateObjectSet<T>();
}
public T Carregar(int id)
{
object objeto;
Contexto.TryGetObjectByKey(GetEntityKey(ObjetoSet, id), out objeto);
return (T)objeto;
}
private static EntityKey GetEntityKey<T>(ObjectSet<T> objectSet, object keyValue) where T : class
{
var entitySetName = objectSet.Context.DefaultContainerName + "." + objectSet.EntitySet.Name;
var keyPropertyName = objectSet.EntitySet.ElementType.KeyMembers[0].ToString();
var entityKey = new EntityKey(entitySetName, new[] { new EntityKeyMember(keyPropertyName, keyValue) });
return entityKey;
}
}
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