Sorting list of strings using linq with custom sort

Question

I am trying to sort a list of strings in an order that is pertinent to a sequence used in common revision history sequences. Some customers start with "-", or "New", or a few other specific codes, and I can use LINQ to define a custom sort order. However, after a drawing has been revised from Rev A all the way through Rev Z, it becomes Rev AA through Rev AZ, then Rev BA through BZ and so forth. How can I sort the following list using LINQ?

I have this as an example block of code:

List<string> revList = new List<string>  { "A", "NC", "New", "AB", "PD", "PD1", 
                                          "PD2", "B", "-", "*", "BB", "NA" };
revList = revList.OrderByDescending(i => i.ToLower() == "pd").
                  ThenByDescending(i => i.ToLower() == "nc").
                  ThenByDescending(i => i.ToLower() == "na").
                  ThenByDescending(i => i.ToLower() == "new").
                  ThenByDescending(i => i.ToLower() == "pd1").
                  ThenByDescending(i => i.ToLower() == "pd2").
                  ThenByDescending(i => i.ToLower() == "-").
                  ThenByDescending(i => i.ToLower() == "*").
                  ThenBy(i => i).ToList();

foreach (string rev in revList)
  Console.WriteLine(rev);

This produces output as:

PD
NC
NA
NEW
PD1
PD2
-
*
A
AB
B
B

I would like to produce:

PD
NC
NA
NEW
PD1
PD2
-
*
A
B
AB
BB

Sort by Length first, e.g. insert ThenBy(i => i.Length). before ThenBy(i => i) — Ivan Stoev
– Ivan Stoev, Commented Feb 22, 2017 at 21:39
Ivan, you win. I wish I could vote for your answer since it was first, but it was a comment. Thank You. — AuLion
– AuLion, Commented Feb 22, 2017 at 22:07
@JonathanWood Obscure details that are really only relevant to our specific numbering requirements. The pertinent part was that I could create a specific sequence of order using LINQ, but I couldn't figure out how to get the subsequent sequence to work in a non alphabetically. — AuLion
– AuLion, Commented Feb 22, 2017 at 22:14

tRuEsAtM · Accepted Answer · 2017-02-22 21:48:33Z

4

This code worked for me.

 var revList = new List<string>  { "A", "NC", "New", "AB", "PD", "PD1",
                                      "PD2", "B", "-", "*", "BB", "NA" };

        revList = revList.OrderByDescending(i => i.ToLower() == "pd").
                          ThenByDescending(i => i.ToLower() == "nc").
                          ThenByDescending(i => i.ToLower() == "na").
                          ThenByDescending(i => i.ToLower() == "new").
                          ThenByDescending(i => i.ToLower() == "pd1").
                          ThenByDescending(i => i.ToLower() == "pd2").
                          ThenByDescending(i => i.ToLower() == "-").
                          ThenByDescending(i => i.ToLower() == "*").
                          ThenBy(i => i.Length).ToList();

        foreach (string rev in revList)
            Console.WriteLine(rev);
        Console.ReadLine();

answered Feb 22, 2017 at 21:48

tRuEsAtM

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1 Comment

AuLion Over a year ago

Thanks, Sameer! I cant believe I didn't think of that.

jce · Accepted Answer · 2017-02-22 21:48:51Z

0

You could create a custom object like this:

class Revision
{
    public string Name { get; set; }
    public int Rank { get; set; }

    public Revision(string Name, int Rank)
    {
        this.Name = Name;
        this.Rank = Rank;
    }
}

Then you can create a list of these objects.

Something like:

List<Revision> revisions = new List<Revision>();
revision.Add(new Revision("PD",1));
revision.Add(new Revision("NC",2));

Now when you can sort by the rank using LINQ instead of trying to parse the names.

It may be a pain to set up the object initially since you may need to go out to ZZ, but this would give you complete control over the order.

p.s. - I didn't test this code.

answered Feb 22, 2017 at 21:48

jce

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