generic repository EF4 CTP5 getById - entity-framework

Question

I have a generic repository an I am trying to add a GetById method as shown here
C# LINQ to SQL: Refactoring this Generic GetByID method
The problem is my repository does not use System.Data.Linq.DataContext
instead I use System.Data.Entity.DbContext
So I get errors where I try to use
Mapping.GetMetaType
and
return _set.Where( whereExpression).Single();
How can I implement a generic GetById method in CTP5? Should I be using System.Data.Entity.DbContext in my Repository.
Here is the start of my repository class
public class BaseRepository<T> where T : class
{
private DbContext _context;
private readonly DbSet<T> _set;
public BaseRepository()
{
_context = new MyDBContext();
_set = _context.Set<T>();
}

Answer 1

The most basic approach is simply
public T GetById(params object[] keys)
{
_set.Find(keys);
}
If you know that all your entities have primary key called Id (it doesn't have to be called Id in DB but it must be mapped to property Id) of defined type you can use simply this:
public interface IEntity
{
int Id { get; }
}
public class BaseRepository<T> where T : class, IEntity
{
...
public T GetById(int id)
{
_set.Find(id);
}
}
If data type is not always the same you can use:
public interface IEntity<TKey>
{
TKey Id { get; }
}
public class BaseRepository<TEntity, TKey> where TEntity : class, IEntity<TKey>
{
...
public TEntity GetById(TKey id)
{
_set.Find(id);
}
}
You can also simply use:
public class BaseRepository<TEntity, TKey> where TEntity : class
{
...
public TEntity GetById(TKey id)
{
_set.Find(id);
}
}

Answer 2

try this
public virtual T GetByID(object id)
{
// Define the entity key values.
IEnumerable<KeyValuePair<string, object>> entityKeyValues =
new KeyValuePair<string, object>[] {
new KeyValuePair<string, object>("Id", id) };
string qualifiedEntitySetName = _context.DefaultContainerName + "." + typeof(T).Name;
EntityKey key = new EntityKey(qualifiedEntitySetName, entityKeyValues);
return (T)_context.GetObjectByKey(key);
}