Question

Given an EntityFramework POCO object model such as:

public class Group
{
    public int GroupID { get; set; }
    public string Category { get; set; }
    public virtual ICollection<Member> Members { get; set; }
}

public class Member
{
    public int MemberID { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Group> Groups { get; set; }
}

Where a Many-To-Many Relationship is defined in the dbContext as follows:

Group      GroupMember   Member
-------    -----------   -------
GroupID    GroupID       MemberID
Category   MemberID      Name

In order to allow group membership maintenance, I want to build a ViewModel that for any requested group, builds a list of all of the ‘Member’ objects in the system, along with a Flag indicating whether the ‘Member’ is already a member of the Group.
The View will display a checkbox for the ‘Flag’ field, and the Member’s Name in a list.

The user will be able to Check/Uncheck the checkbox to edit the list of Members in the Group.

I’ve been spinning my wheels trying to figure out a LINQ query to select this list and would greatly appreciate some pointers.

Answer 1

You mean like:

var model = from m in db.Members
            orderby m.Name
            select new GroupMemberRow
            {
                MemberID = m.MemberID,
                Name = m.Name,
                IsMember = m.Groups.Any(g => g.GroupID == groupId)
            };

?