List Reordering for queue processing

Question

While working on my project I've encountered a little glitch in the way that List works.

I have this list for example:

# Username - Status - Order - Timestamp Admin, Available (int 0), 2, 10:45 User1, Not available (int 2), 1, 10:44 User2, Available, 3, 10:52 User3, Busy (int 1), 4, 10:33

I want a way to order it by multiple properties using something like a comparer.

I would like it to order by Status, so Available comes first, then by Timestamp to know who was first in the list.

So it would output:

Admin, 0, 0, 10:45 User2, 0, 1, 10:52 User3, 1, 2, 10:33 User1, 2, -1, 10:44

The User1 order must become -1 because it is not available so I want it to show last in my list, as busy users comes just before.

I need to keep an order because I want to know who's next. I tried to iterate the old list with ordering it then creating a new one with the good order but it doesn't work.

Here's the method I use:

public static List<ListMember> ReOrder(this List<ListMember> list) { int Index = 0; List<ListMember> newList = new List<ListMember>(); foreach (ListMember member in list.OrderBy(x => x.ListOrder).ThenBy(x => x.DateEntered)) { if (member.DateExited == null) { member.ListOrder = Index; Index++; } else { member.ListOrder = -1; } newList.Add(member); } return newList; }

This is needed because when someone pass from status 1 to 0, he become available but I don't want him to go first, I want him to go last in the list, then reindex the list.

Does someone have an idea on how a list can be greatly ordered.

Are you sure about the output ? User 1 is not available on your example. I would expect User2 before — carndacier
– carndacier, Commented Nov 4, 2015 at 15:58
@M.kazemAkhgary, note that the order #s are also changed from Admin having 2 and User2 having 0 to suddenly Admin having 0 and User2 having -1 that would either suggest some processing being done somewhere, a typo or some other explanation here. — JB King
– JB King, Commented Nov 4, 2015 at 16:10
I think you should review your output or provide a better description of what you want . Why User2 order becomes "-1" ? Why is it in this order ? (User1 before User2) — carndacier
– carndacier, Commented Nov 4, 2015 at 16:11

carndacier · Accepted Answer · 2015-11-04 16:59:54Z

The Sinatr's comment should work.

As far as you need only available items, you can also do :

myList.Where(x => x.Status == 0).OrderBy(y => y.Timestamp)

I'm guessing to do the "Where" first will return a shorter list, then the orderBy would be faster to execute (someone to confirm ?)

Edit

After your edit, I would suggest to do like that :

public static List<ListMember> ReOrder(this List<ListMember> list) { int Index = 0; foreach (ListMember member in list.OrderBy(x => x.DateEntered)) { if (member.DateExited == null) { member.ListOrder = Index; Index++; } else { member.ListOrder = -1; } } return list; }

I think you don't need to create a new list just to update a field. just update it directly in your list.

I would also suggest you to don't call often this function, because if you get a lot of items in your list, it can take time ! You should create a function in your ListMember Class, "SetDateExit". It could be :

public void SetDateExit(DateTime dateExit) { this.DateExited = dateExit; this.ListOrder = -1; }

And then, when you need to display your result, just do like that :

return myList.Where(x => ListOrder != -1).OrderBy(x => x.ListOrder);

I have more that 2 status, I have many of them, but I need to order by the type of the Status, which I only have 3.

Saransh Kataria · Accepted Answer · 2015-11-04 16:11:33Z

You can use dynamic LINQ for ordering by multiple fields. Using Linq.Dynamic, and the NuGet (https://www.nuget.org/packages/System.Linq.Dynamic.Library/) you can use comma separated values to order

myList.OrderBy("Availibility,Timestamp");

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