Entity Framework 4 overwrite Equals and GetHashCode of an own class property
- by Zhok
Hi,
I’m using Visual Studio 2010 with .NET 4 and Entity Framework 4. I’m working with POCO Classes and not the EF4 Generator. I need to overwrite the Equals() and GetHashCode() Method but that doesn’t really work. Thought it’s something everybody does but I don’t find anything about the problem Online.
When I write my own Classes and Equals Method, I use Equals() of property’s, witch need to be loaded by EF to be filled. Like this:
public class Item
{
public virtual int Id { get; set; }
public virtual String Name { get; set; }
public virtual List<UserItem> UserItems { get; set; }
public virtual ItemType ItemType { get; set; }
public override bool Equals(object obj)
{
Item item = obj as Item;
if (obj == null)
{
return false;
}
return item.Name.Equals(this.Name)
&& item.ItemType.Equals(this.ItemType);
}
public override int GetHashCode()
{
return this.Name.GetHashCode() ^ this.ItemType.GetHashCode();
}
}
That Code doesn’t work, the problems are in Equals and GetHashCode where I try to get HashCode or Equal from “ItemType” . Every time I get a NullRefernceException if I try to get data by Linq2Entites.
A dirty way to fix it, is to capture the NullReferenceException and return false (by Equals) and return base.GetHashCode() (by GethashCode) but I hope there is a better way to fix this problem.
I’ve wrote a little test project, with SQL Script for the DB and POCO Domain, EDMX File and Console Test Main Method. You can download it here:
Download
