Difficulty with LINQ Query writing custom sort logic

Question

I have files like Avinash_Create.sql, Avinash_Insert.sql, Avinash_Update.sql , Avinash_Delete.sql.

I need to iterate over the files list and group them based on the name and order by create, insert, update, and delete files.

I am finding it difficult difficult to accomplish. This is what I have so far:

   var userGroups = shortfilenames.GroupBy(s => s.Substring(0, s.IndexOf('_')))
         .Select(g => g.OrderBy(x => x.Substring(x.IndexOf('_')).Contains("CREATE"))
                      .ThenBy(x => x.Substring(x.IndexOf('_')).Contains("INSERT"))
                      .ThenBy(x => x.Substring(x.IndexOf('_')).Contains("UPDATE"))
                      .ThenBy(x => x.Substring(x.IndexOf('_')).Contains("DELETE")));

The above query is grouping by name 'Avinash' but not working for custom ordering. Please help.

Update:

Please see updated query , still it is not sorting properly

Your .Select(g => g.OrderBy...) should be .Select(g => g).Orderby... (although then you don't need the Select at all). In other words, Select what data you want and then OrderBy. — crashmstr
– crashmstr, Commented Sep 16, 2014 at 19:41
@crashmstr I think he is trying to sort each group, so I think his ordering is in the correct place — rdans
– rdans, Commented Sep 16, 2014 at 19:44

rdans · Accepted Answer · 2014-09-16 20:28:10Z

2

Uses Split to extract the relevant sections of the string. Converts the result to upper case, which seems to be missing from your attempt. Additionally makes it a bit shorter by using an array to hold your custom sort order and then Array.IndexOf to get a sort order from it, rather than multiple OrderBy/ThenBy.

var ordering = new [] {"CREATE", "INSERT", "UPDATE", "DELETE"};
var results = shortfilenames.GroupBy(s => s.Split('_')[0])
              .Select(g => g.OrderBy(x => Array.IndexOf(ordering, x.Split('_')[1].Split('.')[0].ToUpper())));

edited Sep 16, 2014 at 20:28

answered Sep 16, 2014 at 19:56

rdans

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2 Comments

Sai Avinash Over a year ago

Giving the error : index and location must refer to same location in the string

Sai Avinash Over a year ago

@Ryan..Simply Amazing :) . Can you please clarify me what is the change that you made now..I am not able to under stand it

Tim Schmelter · Accepted Answer · 2014-09-16 19:46:36Z

1

This seems to be what what you want:

var shortfilenames = new List<string>(){"Avinash_Create.sql" , "Avinash_Insert.sql" , "Avinash_Update.sql" , "Avinash_Delete.sql"};
var userGroups = shortfilenames
    .Select(fn =>
    {
        string fileName = Path.GetFileNameWithoutExtension(fn);
        string[] nameAndAction = fileName.Split('_');
        return new
        {
            extension = Path.GetExtension(fn),
            fileName,
            name = nameAndAction[0],
            action = nameAndAction[1]
        };
    })
    .GroupBy(x => x.name)
    .Select(g => g.OrderByDescending(x => x.action.Equals("CREATE", StringComparison.InvariantCultureIgnoreCase))
                  .ThenByDescending(x => x.action.Equals("INSERT", StringComparison.InvariantCultureIgnoreCase))
                  .ThenByDescending(x => x.action.Equals("UPDATE", StringComparison.InvariantCultureIgnoreCase))
                  .ThenByDescending(x => x.action.Equals("DELETE", StringComparison.InvariantCultureIgnoreCase))
                  .ToList());

foreach (var ug in userGroups)
foreach (var x in ug)
    Console.WriteLine("{0} {1}", x.name, x.action);

prints out:

Avinash Create
Avinash Insert
Avinash Update
Avinash Delete

Presumes that the file-names always contain the underscore.

answered Sep 16, 2014 at 19:46

Tim Schmelter

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2 Comments

Sai Avinash Over a year ago

@Tim..This is sorting great..Thanks for that. but can i just get the file names in the sorted order instead of name and action ?

Tim Schmelter Over a year ago

@SaiAvinash: i don't understand, you can access all properties of the anonymous type. So just use x.fileName instead of x.name or x.action

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