GUID or int entity key with SQL Compact/EF4?
Posted
by David Veeneman
on Stack Overflow
See other posts from Stack Overflow
or by David Veeneman
Published on 2010-03-20T18:20:40Z
Indexed on
2010/03/20
18:31 UTC
Read the original article
Hit count: 229
This is a follow-up to an earlier question I posted on EF4 entity keys with SQL Compact. SQL Compact doesn't allow server-generated identity keys, so I am left with creating my own keys as objects are added to the ObjectContext
. My first choice would be an integer key, and the previous answer linked to a blog post that shows an extension method that uses the Max
operator with a selector expression to find the next available key:
public static TResult NextId<TSource, TResult>(this ObjectSet<TSource> table, Expression<Func<TSource, TResult>> selector)
where TSource : class
{
TResult lastId = table.Any() ? table.Max(selector) : default(TResult);
if (lastId is int)
{
lastId = (TResult)(object)(((int)(object)lastId) + 1);
}
return lastId;
}
Here's my take on the extension method: It will work fine if the ObjectContext
that I am working with has an unfiltered entity set. In that case, the ObjectContext
will contain all rows from the data table, and I will get an accurate result. But if the entity set is the result of a query filter, the method will return the last entity key in the filtered entity set, which will not necessarily be the last key in the data table. So I think the extension method won't really work.
At this point, the obvious solution seems to be to simply use a GUID as the entity key. That way, I only need to call Guid.NewGuid()
method to set the ID property before I add a new entity to my ObjectContext
.
Here is my question: Is there a simple way of getting the last primary key in the data store from EF4 (without having to create a second ObjectContext
for that purpose)? Any other reason not to take the easy way out and simply use a GUID? Thanks for your help.
© Stack Overflow or respective owner