C#

public class Group
{
    private List users;
    public List Users
    {
        get { 
            if (users==null) users=new List();
            return users;
        }
    }
    //constructor selects users from database, populates "users" with new User()
}

class User {
    private static List<User> users=new List<User>();

    public User() {
        users.Add(this);
    }
}

public sealed class UserGroupManager
{
    public UserGroupManager
    (
        Test DataContext
    )
    {
        this.Users = new System.Collections.Generic.HashSet<Test.User>() ;

        this.Groups = new System.Collections.Generic.HashSet<Test.Group>() ;

        foreach
        (
            Test.User user
        in
            DataContext.Users
        )
        {
            foreach
            (
               Test.Group group
            in
                DataContext.ExecuteQuery<Test.Group>
                (
                    @"SELECT [Group].* FROM UserGroup INNER JOIN [Group] ON UserGroup.GroupID=[Group].ID WHERE UserGroup.UserID=?"
                ,
                    user.ID
                )
            )
            {
                group.Users.Add ( user ) ;
                user.Groups.Add ( group ) ;

                this.Groups.Add ( group ) ;
            }

            this.Users.Add ( user ) ;
        }

        return ;
    }

    public readonly System.Collections.Generic.HashSet<Test.User> Users ;

    public readonly System.Collections.Generic.HashSet<Test.Group> Groups ;
}

devvvy wrote:

This makes it kind of useless as if jobs are quick to execute you wouldn't really need to have it placed on a thread in the first place.

this.Invoke(()=> this.Visible = false; );

devvvy wrote:

Also, what really are the negative consequences for putting long running jobs on dotnet ThreadPool's threads?

I are Troll

devvvy wrote:

My question is, why. Why dotnet ThreadPool is only for quick executions? This makes it kind of useless as if jobs are quick to execute you wouldn't really need to have it placed on a thread in the first place.