Question

I am trying to create 3 different lists (1,2,3) from 2 existing lists (A,B).
The 3 lists need to identify the following relationships.

• List 1 – the items that are in list A and not in list B
• List 2 – the items that are in list B and not in list A
• List 3 – the items that are in both lists.

I then want to join all the lists together into one list.

My problem is that I want to identify the differences by adding an enum identifying the relationship to the items of each list. But by adding the Enum the Except Linq function does not identify the fact (obviously) that the lists are the same. Because the Linq queries are differed I can not resolve this by changing the order of my statements ie. identify the the lists and then add the Enums.

This is the code that I have got to (Doesn’t work properly)
There might be a better approach.

        List<ManufactorListItem> manufactorItemList =
           manufactorRepository.GetManufactorList();

        // Get the Manufactors from the Families repository
        List<ManufactorListItem> familyManufactorList =
            this.familyRepository.GetManufactorList(familyGuid);

        // Identify Manufactors that are only found in the Manufactor Repository
        List<ManufactorListItem> inManufactorsOnly =
            manufactorItemList.Except(familyManufactorList).ToList();

        // Mark them as (Parent Only)
        foreach (ManufactorListItem manOnly in inManufactorsOnly) {
            manOnly.InheritanceState = EnumInheritanceState.InParent;
        }

        // Identify Manufactors that are only found in the Family Repository
        List<ManufactorListItem> inFamiliesOnly =
            familyManufactorList.Except(manufactorItemList).ToList();

        // Mark them as (Child Only)
        foreach (ManufactorListItem famOnly in inFamiliesOnly) {
            famOnly.InheritanceState = EnumInheritanceState.InChild;
        }

        // Identify Manufactors that are found in both Repositories
        List<ManufactorListItem> sameList =
            manufactorItemList.Intersect(familyManufactorList).ToList();

        // Mark them Accordingly
        foreach (ManufactorListItem same in sameList) {
            same.InheritanceState = EnumInheritanceState.InBoth;
        }

        // Create an output List
        List<ManufactorListItem> manufactors = new List<ManufactorListItem>();

        // Join all of the lists together.
        manufactors = sameList.Union(inManufactorsOnly).
            Union(inFamiliesOnly).ToList();

Any ideas hot to get around this?
Thanks in advance

Answer 1

You can make it much simplier:

List<ManufactorListItem> manufactorItemList = ...;
List<ManufactorListItem> familyManufactorList = ...;
var allItems = manufactorItemList.ToDictionary(i => i, i => InheritanceState.InParent);

foreach (var familyManufactor in familyManufactorList)
{
    allItems[familyManufactor] = allItems.ContainsKey(familyManufactor) ?
                                 InheritanceState.InBoth : 
                                 InheritanceState.InChild;
}

//that's all, now we can get any subset items:  

var inFamiliesOnly = allItems.Where(p => p.Value == InheritanceState.InChild).Select(p => p.Key);
var inManufactorsOnly = allItems.Where(p => p.Value == InheritanceState.InParent).Select(p => p.Key);
var allManufactors = allItems.Keys;