title: Determine if an int value exists once in an array
body: <p>I know you can use Any, Exists, and Single with LINQ but can't quite get this to work.  I need to do a lookup based on an id to see if it's in the array and make sure that there is only ONE match on that value.  because if there are 2 it's gonna cause an issue..the requirement that I'm checking is that the array only has one and only one of each ID in the array.</p>
  
  <p>Here's what I tried</p>
  
  <pre><code>if(someIntArray.Single(item =&gt; item = 3)
      //... we found the value 8 in the array only once so now we can be confident and do something 
  </code></pre>