There are multiple related questions, but I'm looking for a solution specific to my case. There is an array of (usually) 14 integers. How can I quickly tell if each int appears exactly twice (i.e. there are 7 pairs)? The value range is from 1 to 35. The main aspect here is performance.

For reference, this is my current solution. It was written to resemble the spec as closely as possible and without performance in mind, so I'm certain is can be improved vastly:

```
var pairs = Array
    .GroupBy (x => x)
    .Where (x => x.Count () == 2)
    .Select (x => x.ToList ())
    .ToList ();
IsSevenPairs = pairs.Count == 7;

```

Using Linq is optional. I don't care how, as long as it's fast :)

**Edit:** There is the special case that an int appears 2n times with n > 1. In this case the check should *fail*, i.e. there should be 7 distinct pairs.

**Edit: Result**
I tested Ani's and Jon's solutions with tiny modifications and found during multiple benchmark runs in the target app that Ani's has about twice Jon's throughput on my machine (some Core 2 Duo on Win7-64). Generating the array of ints already takes about as long as the respective checks, so I'm happy with the result. Thanks, all!