Question

This is the data in my database table:

That’s my business object:

public class Unit
    {
        public Unit()
        {
            MemberIdList = new List<String>();
        }

        public String UnitType { get; set; }
        public String UnitZoom { get; set; }
        public String MemberZoom { get; set; }

        public List<String> MemberIdList { get; set; }
    }

The whole data from database is fetched and put into a DataTable.

Now comes the Linq Transformation…

After I return a List with 3 Unit objects holding this data:

Now guess how I got the data into the 3 business objects…
that’s the way I would like to know. A hint might be Distinct and IEqualityComparer for the 3 properties…
just an assumption…

UPDATE

Question updated:

Please read the comment in the code 🙂

var groupedCollection = table.AsEnumerable()
                                    .GroupBy(row => new
                                    {
                                        UType = row.Field<string>("UnitType"),
                                        UZoom = row.Field<string>("UnitZoom"),
                                        MZoom = row.Field<string>("MemberZoom"),
                                        MOrder = row.Field<int>("MemberOrder"), 

// I DO NOT WANT the MemberOrder to be in the Group Key, but later on I use this Property to order by it…
});

            var unitCollection = groupedCollection
                                .Select(g => new Unit 
                                {
                                    UnitType = g.Key.UType,
                                    UnitZoom = g.Key.UZoom,
                                    MemberZoom = g.Key.MZoom,                                   
                                    MemberIdList = g.Select(r => r.Field<string>("MemberId")).OrderBy(b => g.Key.MOrder).ToList(),
                                });

            List<Unit> units = unitCollection.ToList(); 

Answer 1

Something like this ?

DataTable dt = ...

var list = 
dt.AsEnumerable()
.GroupBy(r => new
{
    UType = r.Field<string>("UnitType"),
    UZoom = r.Field<string>("UnitZoom"),
    MZoom = r.Field<string>("MemberZoom")
})
.Select(g => new Unit 
{ 
    UnitType = g.Key.UType, 
    UnitZoom = g.Key.UZoom, 
    MemberZoom = g.Key.MZoom ,
    MemberIdList = g.Select(r => r.Field<string>("MemberId")).Distinct().ToList()
})
.ToList();

EDIT:
the call to .Distinct() is not strictly necessary. It avoids duplicated MemberIds if you can have them, but it really depends on what OP needs.

EDIT2:
(according to the last question update)

You are close to the solution:

just change this line of my code:

MemberIdList = g.Select(r => r.Field<string>("MemberId")).ToList()

to:

MemberIdList = g.Select(r => r.Field<string>("MemberId")).OrderBy(r => r.Field<int>("MOrder")).ToList()