Question

I’m making a project for my work, and there is a big problem…
I’m making a software that takes information about users from a CSV(coma separate values) file. Every user has own phone number and a number that he was called. When the inforamtion is gathered from the file, i want to take the all phone numbers that are for a number and sort them ascending. I want not to be all ocurance of phone number, just this that are with big duration to be up. That means like that:

1-345345-9375683027
2-345345-3070982743
3-345345-9375683027
4-345345-3070982743
5-345345-9375683027
6-345345-2389479734
7-345345-2349875993

Number 1, 3 and 5 are equals.
Number 2 and 4 are equals.
I want to sort the number like this:

1-345345-9375683027
2-345345-3070982743
3-345345-2389479734
4-345345-2349875993

Now 1 us the most common, 2 is less comon that first and so one…
I was trying any thing but without problem.
Like this one:

var result = user.transactions.where(x=>x.phone == user.phone);

If you want to look at the project that i’m making here is the solution file:
http://mtelanalyzer.codeplex.com/

Answer 1

Assuming the phone numbers are a List<String>:

var result = phoneNumbers.GroupBy(pn => pn)
             .Select(grp => new { Number = grp.Key, Count = grp.Count() })
             .OrderByDescending(x => x.Count)
             .Select(x => x.Number);

1. group by phone-number
2. select an anonymous type to be able to order by the count
3. order by descending(highest occurence first), then by the number
4. select the number, the result is an IEnumerable<String> (or whatever type it is)

Edit: I’ve only just seen that you’re ordering as second not by number but by the index. That makes it a little bit more complicated:

var result = phoneNumbers.Select((pn, i) => new { Number = pn, Index = i })
             .GroupBy(x => x.Number)
             .Select(grp => new { 
                 Number = grp.Key, 
                 Count  = grp.Count(), 
                 Index  = grp.First().Index 
             })
             .OrderByDescending(x => x.Count)
             .ThenBy(x => x.Index)
             .Select(x => x.Number);