LINQ query that combines grouping and sorting

Question

I am relatively new to LINQ and currently working on a query that combines grouping and sorting. I am going to start with an example here. Basically I have an arbitrary sequence of numbers represented as strings:

List<string> sNumbers = new List<string> {"34521", "38450", "138477", "38451", "28384", "13841", "12345"}

I need to find all sNumbers in this list that contain a search pattern (say "384") then return the filtered sequence such that the sNumbers that start with the search pattern ("384") are sorted first followed by the remaining sNumbers that contain the search pattern somewhere. So it will be like this (please also notice the alphabetical sort with in the groups):

{"38450", "38451", "13841", "28384", "138477"}

Here is how I have started:

outputlist = (from n in sNumbers
                where n.Contains(searchPattern
                select n).ToList();

So now we have all number that contain the search pattern. And this is where I am stuck. I know that at this point I need to 'group' the results into two sequences. One that start with the search pattern and other that don't. Then apply a secondary sort in each group alphabetically. How do I write a query that combines all that?

Answer 1

I think you don't need any grouping nor list splitting for getting your desired result, so instead of answer about combining and grouping I will post what I would do to get desired result:

sNumbers.Where(x=>x.Contains(pattern))
    .OrderByDescending(x => x.StartsWith(pattern)) // first criteria
    .ThenBy(x=>Convert.ToInt32(x)) //this do the trick instead of GroupBy
    .ToList();

Answer 2

This seems fairly straight forward, unless I've misunderstood something:

List<string> outputlist = 
    sNumbers
        .Where(n => n.Contains("384"))
        .OrderBy(n => int.Parse(n))
        .OrderByDescending(n => n.StartsWith("384"))
        .ToList();

I get this:

Answer 3

var result = sNumbers
                        .Where(e => e.StartsWith("384"))
                        .OrderBy(e => Int32.Parse(e))
                .Union(sNumbers
                        .Where(e => e.Contains("384"))
                        .OrderBy(e => Int32.Parse(e)));