I have question about how I could use Linq grouping the same combination that the list has then relate to a two list.

Example:

I have theses classes.

public class PetCategoryOwner
{
    public string PetCategory { get; set; }
    public string Owner { get; set; }
}

public class PetCategoriesOwners
{
    public IEnumerable<string> PetCategories { get; set; }
    public IEnumerable<string> Owners { get; set; }
}

The example data.

var petCategoryOwner = new List<PetCategoryOwner>()
{
    new PetCategoryOwner { Owner = "Higa", PetCategory = "Terry"},
    new PetCategoryOwner { Owne = "Higa", PetCategory = "Charlotte"},
    new PetCategoryOwner { Owne = "Oliver", PetCategory = "Terry"},
    new PetCategoryOwner { Owne = "Oliver", PetCategory = "Charlotte"},
    new PetCategoryOwner { Owne = "Oliver", PetCategory = "Chausie"},
    new PetCategoryOwner { Owner = "Price", PetCategory = "Chausie"},
    new PetCategoryOwner { Owner = "Liam", PetCategory = "Terry"},
    new PetCategoryOwner { Owner = "Liam", PetCategory = "Chartreux"}
};

Expected values

var petCategoriesOwners = new List<PetCategoriesOwners>()
{
    new PetCategoriesOwners()
    {
        PetCategories = new List<string>() { "Terry", "Charlotte" },
        Owners = new List<string>() { "Oliver", "Higa" }
    },
    new PetCategoriesOwners()
    {
        PetCategories = new List<string>() { "Chausie" },
        Owners = new List<string>() { "Oliver", "Price" }
    },
    new PetCategoriesOwners()
    {
        PetCategories = new List<string>() { "Chartreux", "Terry" },
        Owners = new List<string>() { "Liam" }
    }
}

CodePudding user response：

In order to solve your problem you need to do two steps: group by owners and merge owners based on the fact other group's set is a subset of current owner. You can try to achieve it by running below LINQ query:

public class PetCategoriesOwners
{
    public List<string> PetCategories { get; set; }
    public List<string> Owners { get; set; }
}

var petCategoriesOwners = petCategoryOwner
    .GroupBy(x => x.Owner)
    .Select(x => new
    {
        Owner = x.Key,
        Categories = x.Select(y => y.PetCategory)
    })
    .OrderBy(x => x.Categories.Count())
    .Aggregate(new List<PetCategoriesOwners>(), (acc, current) =>
    {
        var currentCategories = current.Categories.ToList();
        var matches = acc.Where(group => group.PetCategories.All(x => currentCategories.Contains(x)));

        foreach(var match in matches)
        {
            match.Owners.Add(current.Owner);
            currentCategories = currentCategories.Except(match.PetCategories).ToList();
        }

        if (currentCategories.Any())
        {
            acc.Add(
                new PetCategoriesOwners() { 
                    Owners = new List<string>() { current.Owner }, 
                    PetCategories = currentCategories 
                });
        }

        return acc;
    });

So it's important to group by Owner, process groups in ascending order in terms of length. The Aggregate method basically tries to find if previosly entered item overlaps with currently processed one. If it happens then we take those intersecting elements, add owner there and remove those from current element. If any element is left then we create own group for such owner.

CodePudding user response：

You could achieve what you want to do by using a combination of SelectMany(), .Select(), .Where() and .Contains() from System.Linq.

Slightly simplified, by using ints for the group value rather than char, this is a possible implemenation:

public class GroupedOwnerAndPetCategory
{
    public string Owner { get; set; }
    public string PetCategory { get; set; }
    public int Group { get; set; }
}

var grouped = petCategoriesOwners
    .SelectMany((ownerPetMix, index) => petCategoryOwner
        .Where(ownerPetPair =>
                ownerPetMix.Owners.Contains(ownerPetPair.Owner) &&
                ownerPetMix.PetCategories.Contains(ownerPetPair.PetCategory))
        .Select(ownerPetPair => new GroupedOwnerAndPetCategory
            {
                Owner = ownerPetPair.Owner,
                PetCategory = ownerPetPair.PetCategory,
                Group = index
            }))
    .ToList();

Using your example input, grouped contains the following entries:

Higa      Terry        0
Higa      Charlotte    0
Oliver    Terry        0
Oliver    Charlotte    0
Oliver    Chausie      1
Price     Chausie      1
Liam      Terry        2
Liam      Chartreux    2

Example fiddle here.