Exception in NHibernate query when use Contains

Question

I have the following classes:

class Operation
{
    User User_AssignedTo;
    ResourceGroup ResourceGroup;
} 

class ResourceGroup
{
    List<User> UsersCollection;
}

And I have method. It takes user and returns operations. Something like that:

ResourceGroup resourceGroup = null;

query = conn.Session.QueryOver<Operation>()
        .JoinAlias(item => item.ResourceGroup, () => resourceGroup)
        .Where(item => item.User_AssignedTo.Id == user.Id || resourceGroup.UsersCollection.Contains(userDm));

but I have exception

Unrecognised method call: System.Collections.Generic.ICollection`1[[Mapping.Classes.User, Mapping.Classes, Version=1.0.0.0, Culture=neutral, PublicKeyToken=8ab89f53b66a52c3]]:Boolean Contains

Answer 1

The Contains is a C# function. In SQL we would use the MyProperty IN (Select ...). To achieve that with NHibernate, to have the IN clause and the inner select - we can use the DetachedCriteria:

The documentation: 15.8. Detached queries and subqueries

There are some detailed examples how to use it:

• Detailed how to, and advantages of the inner select (e.g. paging)
• Inner select with group by cluase (e.g. to filter by select Max(id))

NOTE: I would like to provide you with more details even for your solution, some draft.. But the problem is the snippets in the question. To be able to use IN both parts should have some ID (the 1) ID to selected and 2) the ID to be compared). ResourceGroup is missing ID, hard to understand how the pairing tables behind are designed.

But at least the DetachedCriteria concept should give you correct direction...