Sort list by field (C#)

Question

I have class like:

class SortNode
{
    public Int32 m_valRating = 0;

    public SortNode(Int32 valRating)
    {
        this.m_valRating = valRating;
    }
}

and some list refSortNodeList:

List<SortNode> refSortNodeList = new List<SortNode>();

Random refRandom = new Random();

for (int i = 0; i < 100; ++i)
{
    refSortNodeList.Add(new SortNode(refRandom.Next(-10, 30)));
}

foreach (var varSortNode in refSortNodeList)
{
    Console.WriteLine("SortNode rating is {0}", varSortNode.m_valRating);
}

How to sort easily my refSortNodeList by m_valRating field? Or maybe I need to use some another List class?

Public fields are a bad idea, btw – Marc Gravell Mar 28 '11 at 15:45 — Marc Gravell, Mar 28 '11 at 15:45

score 82 · Accepted Answer · answered Mar 28 '11 at 15:43

82

list.Sort((x,y) =>
    x.m_valRating.CompareTo(y.m_valRating));

answered Mar 28 '11 at 15:43

Marc Gravell

1,026,079
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2

Throws if it compares a null though. – Jon Hanna Mar 28 '11 at 15:47
3

@Jon - youcan of course code around that, but a null here would probably be an error anyway – Marc Gravell Mar 28 '11 at 15:49
True I've just hit enough comparison-with-null-in-sort bugs to be doubly paranoid about them, but they shouldn't happen here, you are right. – Jon Hanna Mar 28 '11 at 16:03

score 20 · Answer 2 · answered Mar 28 '11 at 15:45

In-place:

refSortNodeList.Sort(
  (x, y) =>
    x == null ? (y == null ? 0 : -1)
      : (y == null ? 1 : x.m_valRating.CompareTo(y.m_valRating))
);

Creating a new enumeration:

var newEnum = refSortNodeList.OrderBy(x => x.m_valRating);

Creating a new list:

var newList = refSortNodeList.OrderBy(x => x.m_valRating).ToList();

In-place is fastest and most memory efficient, but no good if you want to also retain the old list.

The next is faster than the last and gives results as they go, but you have to re-do the sort to use it again, in which case the third is the one to go for.

score 14 · Answer 3 · edited Dec 20 '13 at 10:50

Use Linq order by.

var mySortedList = refSortNodeList.OrderBy(x => x.m_valRating);

Here is a real live example where I am pulling a list from a database but it is exactly the same concept.

 vendorProducts = (from vp in db.COMPANIES_VND_PRODUCTS
                    join p in db.CT_CT_INV_CLASSES on vp.CLASS_ID equals p.CLASS_ID
                    join m in db.CT_CT_MODALITY_CODES on vp.MODALITY_ID equals m.MODALITY_ID
                    where vp.COMPANY_ID == companyId
                    select new ProductTypeModality
                    {
                      Active = p.ACTIVE.Equals("Y") ? true : false,
                      BioMedImaging = p.BIOMED_IMAGING,
                      Code = p.CLASS_CODE,
                      Description = p.DESCRIPTION,
                      Id = p.CLASS_ID,
                      PricingMargin = p.PRICING_MARGIN,
                      ModalityCode = m.MODALITY_CODE,
                      ModalityId = m.MODALITY_ID,
                      VendorId = companyId
                    }).OrderBy(x => x.Code).ToList<ProductTypeModality>();

score 2 · Answer 4 · answered Mar 28 '11 at 15:42

2

Implement IComparable<T>

answered Mar 28 '11 at 15:42

Daniel A. White

187,200
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score 2 · Answer 5 · answered Mar 28 '11 at 15:44

2

You can use Linq for basic sorts:

refSortNodeList.OrderBy(n => n.m_valRating);

If you need more complex sorting your will need to implement IComparable to use the built in sorting.

answered Mar 28 '11 at 15:44

Kelsey

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score 1 · Answer 6 · answered Mar 28 '11 at 15:46

1

Try this:

refSortNodeList.Sort(new delgate(SortNode x, SortNode y)
   {
       return x.CompareTo(y);
    }
);

answered Mar 28 '11 at 15:46

Mike Marshall

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score 0 · Answer 7 · answered Mar 28 '11 at 15:43

0

It's easy using linq:

var newlist = refSortNodeList.sort( n => n.m_valRating );

answered Mar 28 '11 at 15:43

dcarneiro

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`Sort()` does not return value and `OrderBy()` does not return list. – mgronber Mar 28 '11 at 15:50
OrderBy returns an IOrderedEnumerable (http://msdn.microsoft.com/en-us/library/bb534966.aspx) – dcarneiro Mar 28 '11 at 15:53

score 0 · Answer 8 · answered Mar 28 '11 at 16:05

List<SortNode> refSortNodeList = new List<SortNode> ();

Random refRandom = new Random ();

for (int i = 0; i < 100; ++i) {
    refSortNodeList.Add (new SortNode (refRandom.Next (-10, 30)));
}

// Use this (Linq) if you're using .NET 3.5 or above.
var sortedList = refSortNodeList.OrderBy (node => node.m_valRating);
foreach (var varSortNode in sortedList) {
    Console.WriteLine ("SortNode rating is {0}", varSortNode.m_valRating);
}

// Use this otherwise (e.g. .NET 2.0)
refSortNodeList.Sort (
    delegate (SortNode n1, SortNode n2) {
        return n1.m_valRating.CompareTo (n2.m_valRating);
    }
);

foreach (var varSortNode in refSortNodeList) {
    Console.WriteLine ("SortNode rating is {0}", varSortNode.m_valRating);
}

Sort list by field (C#)

8 Answers8

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