How to group 2 different sequences in LINQ?

Question

How can I group two different (first typeof years == IEnumerable<string> and second typeof occurs = IEnumerable<int> ) sequences into 1 sequence by the next key: if number in occurs are same, then order by years , else order by occurs using only LINQ ?

I've got these sequences in the following way:

var years  = some_strings.Select(x => x.Split(' ')[1]);
var occurs = years.Select(x => years.Count(e => e == x));

So variable years contains only strings with years and occurs contains count of same years in first sequence.

I cannot understand these techniques in LINQ .

Will I do something like this?

occurs.GroupBy(x => x ???

Where should I use the second sequence? Maybe I can got these sequences in 1 query and then process it?

UPD

I modified my 2 queries in 1 by using anonymous class(?):

    some_strings.Select(x => x.Split(' ')[1]).
    GroupBy(x => x).
    Select(x => new {num = x.Key, count = x.Count() })

So, there are years and occurs both in it.

I'm trying to get next string:

1 1990
1 1991
1 1992
2 1967
2 1968
5 2010
...

Now, having query with needed values, how can I sort it like foregoing clause?

Answer 1

You're pretty close. This should give you a list of strings similar to your latest update:

var occurences
    = years.GroupBy(x => x)
           .Select(x => new { Year = int.Parse(x.Key), Count = x.Count() })
           .OrderBy(x => x.Count)
           .ThenBy(x => x.Year)
           .Select(x => string.Concat(x.Count, " ", x.Year))
           .ToList();

Using the anonymous type you created, you can:

• order by count
• then by year
• and finally create a list of strings using string.Concat

(Note that int.Parse will throw an exception if any of your strings in years are not actually numbers)