C# sorting part of an array based on another array-CodePudding

I have an array of a class that is representing a user and another array of a class that is representing pinned items (currently only user ids). Here are the classes:

public class User
{
    public int UserId { get; set; }
    public bool Pinned { get; set; }

    public User(int userId, bool pinned)
    {
        UserId = userId;
        Pinned = pinned;
    }
}

public class PinnedItem
{
    public int UserId { get; set; }

    public PinnedItem(int userId)
    {
        UserId = userId;
    }
}

All user ids of pinned users are saved in a specific order (order of pinned items) and I want to order the array of users so that pinned users are on top and those pinned users follow the order of pinned items array. So for example, if I have an array of users like:

var users = []{ new User(1, true), new User(2, false), new User(3, true) }

and a pinned items array that looks like this:

var pinnedItems = new [] { new PinnedItem(3), new PinnedItem(1) }

then I want the resulting array to look like this:

[ {3, true}, {1, true}, {2, false} ]

Any kind of help will be very much appreciated. Also if there is anything unclear in the question, I am sorry and will edit it accordingly if need be.

CodePudding user response：

It's a bit scruffy, but something like this will do it:

var joined = 
   users
      .GroupJoin(pinnedItems, u => u.UserId, p => p.UserId, (u, p) => new { u.UserId, Pinned = p.Any() })
      .OrderByDescending(r => r.Pinned)
      .ThenByDescending(r => r.UserId)
      .ToList();

You can tune the projections and sorting to get it just how you want it.

CodePudding user response：

Im sure there are alot of ways to do this, I have alot of LINQ left to learn but the following should get you started;

// First, get the users that are mentioned by a PinnedItem 
var pinnedUsers = pinnedItems.Select(x => users.FirstOrDefault(y => y.UserId == x.UserId));
// Get all the users that are not mentioned in a PinnedItem
var unpinnedUsers = users.Except(pinnedUsers);
// Combine both
var both = pinnedUsers.Concat(unpinnedUsers);