Sort List<T> with an array

Question

Basically I have a list containing all items. Then I have a string containing the IDs I want to grab out from the list, to do this I split the string into an Int array and later use this and LINQ to get the items I want from the list

Like this :

List<T> lstAllList = Model.getAllItems();

string stringIDs = "8,9,12,11,7";

int[] intArray = stringIDs.Split(',').Select(n => Convert.ToInt32(n)).ToArray();

List<T> lstLimitedList = (from r in lstAllList where intArray.Contains(r.id) select r).ToList();

Which works great.

But the issue here is that I want to have my list ordered in the same way as the string of IDs is, i.e 8,9,12,11,7 like in this example. But the returned list from the LINQ sorts it by the id by default, so the returned list is 7,8,9,11,12.

Is there a way to prevent it from sorting it like this or is there a way to sort the new list with my int array?

D Stanley · Accepted Answer · 2014-04-29 12:49:49Z

3

Sure, just sort by the index of the ID in the array:

string stringIDs = "8,9,12,11,7";

int[] intArray = stringIDs.Split(',').Select(n => Convert.ToInt32(n)).ToArray();

var lstLimitedList = (
        from r in lstAllList 
        where intArray.Contains(r.id) 
        orderby Array.IndexOf(intArray, r.id)   // <--------
        select r).ToList();

answered Apr 29, 2014 at 12:49

D Stanley

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1 Comment

HenrikP Over a year ago

Well this was easier than expected. Will accept the answer when it becomes available. Thanks!

Yves Dubois · Accepted Answer · 2014-04-29 12:54:50Z

1

Simply getting the elements one at a time may be faster than trying to resort. (Anyone willing to calculate the O() costs?)

List<T> lstLimitedList = new List<T>();

foreach(int id in intArray)
{
    lstLimitedList.Add(lstAllList.Where(item => item.id = id));
}

You could also use intArray.ForEach() if you're a LINQ maniac, but this is much easier to read. ;)

answered Apr 29, 2014 at 12:54

Yves Dubois

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Comments

y0j0 · Accepted Answer · 2014-04-29 13:06:13Z

1

Try to rotate your query. Under word rotate I mean start with intArray and use join. Something like this:

List<T> lstLimitedList = (
from id in intArray 
join item in lstAllList on id equals item.Id 
select item).ToList();

answered Apr 29, 2014 at 13:06

y0j0

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Comments

brumScouse · Accepted Answer · 2014-04-29 12:56:05Z

0

Id use the intersect extension method with provided by LINQ!

int[] array ={ 8,9,12,11,7} // or your result from your split on string;
List<int> array2 = new List<int> { 8,9,12,11,7 } // your model.GetAllItems;

// Call Intersect extension method.
var intersect = array.Intersect(array2);
// Write intersection to screen.
foreach (int value in intersect)
{
    Console.WriteLine(value); // Output: 8,9,12,11,7 
}

Bit cleaner for me

edited Apr 29, 2014 at 12:56

user27414

answered Apr 29, 2014 at 12:55

brumScouse

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Georgi-it · Accepted Answer · 2014-04-29 12:51:58Z

-2

Stop overusing LINQ guys. In this case linq is a total overkill. A much simpler and better performance-wise solution is the following:

string a = "8,9,12,11,7";

List<int> list = new List<int>();

string[] splitted = a.Split(',');
for (int i = 0; i < splitted.Length; i++)
{
    list.Add(int.Parse(splitted[i]));
}

Which a single loop and without sorting etc.

answered Apr 29, 2014 at 12:51

Georgi-it

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3 Comments

Georgi-it Over a year ago

So you are not even gonna defend your -1's against this working easy solution ?

D Stanley Over a year ago

The end result should be a list of Ts (whatever that is), not a list of ints.

user27414 Over a year ago

The OP is trying to sort based on the order of the values in his array. You provided an alternative way of getting the array in the first place. You have not answered the question.

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