使用nhibernate获取通用数据

Question

I wanna create universal/generic method for getting data from various entities. This is my code...

public T GetOldData<T>(ISession session, object id) where T : class
{
     var data = session.Get<T>(id);

     return data;
}

...but I allways got this error:

Ambiguous persister for System.Object implemented by more than one hierarchy.

I call it with: var data = GetOldData<object>(session, @event.Entity);

Answer 1

When you pass the object to your Get<> generic method, NHibernate does not know what mapped entity you need. What you have to do is to provide what entity you need, for sample:

var data = GetOldData<Customer>(session, customerId);

You also could implement a method to provide a type instead of a generic. For sample:

var entityType = typeof(Customer); // or something dynamic

var data = (Customer) GetOldData(session, entityType, id);

And implement the method:

public object GetOldData(ISession session, Type entityType, object id) 
{
     var data = session.Get(entityType, id);

     return data;
}