LINQ custom sort using comparer

Question

I have a class:

public class Item
{
  public int ownerID;
  public decimal value;
}

And an array of objects

Item[] items;

That looks like:

ownerID     value
476478      0.65
636566      0.2

And I have a second class

public class Owner
{
  public int ownerID;
  public int index;
}

And an array of objects

Owner[] owners;

The "owners" is sorted in specific order according the index and looks like:

ownerID    index
636566     1
476478     2

How can I sort the "items" in the same order as the "owners" using LINQ and comparer?

Would expect something like:

items = items.OrderBy(o => o.OwnerID, comparer(o))

where comparing made by "index".

Thanks a lot.

Answer 1

Assuming what you're trying to do is to order the items using the index property from the Owner object, something like this should do the job:

var joined = items.Join(owners, item => i.OwnerId, owner => o.OwnerId, (item, owner) => new
{
    Item = item,
    Index = owner.Index
});

var orderedItems = joined.OrderBy(j => j.Index).Select(j => j.Item);

Answer 2

Try this

//Initiate new object 
    Item items= new Items(); 
//Sort the items based on owner ID 
List myList = items.OrderBy(x => x.ownerID).ToList();  

Answer 3

You can turn your Owner array into a Dictionary<int, int> like this:

Dictionary<int, int> ownerDict = owners.ToDictionary(x => x.ownerID, y => y.index);

And then use that to order the items like:

Item[] orderedItems = items.OrderBy(i => ownerDict[i.ownerID]).ToArray();

To order the items by the same index, the owners are ordered.

Answer 4

You can use LINQ .Select(), it will use a collection iterator to process the collection in its natural order. The lambda inside the Select can then be used to fetch each corresponding item from items. Like this:

var itemsInOrder = owners
    .Select(x => items.First(item => item.ownerId == x.ownerId))
    .ToArray();

This assumes that every ownerId can be found in items. If that is not true then you will have to extend it a little, e.g. like this:

var itemsInOrder = owners
    .Select(x => items.FirstOrDefault(item => item.ownerId == x.ownerId))
    .Where(item => item != null)
    .ToArray();