title: Can someone explain why I'm getting an ambiguous invocation error for this?
body: <p>I have a simple object that I'm creating a collection of.  From that collection I need to find duplicates that have the same TransitMapSegmentID.</p>
  
  <pre><code>public class LineString
  {
      public int TransitLineID { get; set; }
      public string TransitLineName { get; set; }
      public int TransitMapSegmentID { get; set; }
      public string HexColor { get; set; }
      public double[][] Coordinates { get; set; }
  }
  
  var lineStrings = new List&lt;LineString&gt;();
  </code></pre>
  
  <p>With the code below I'm getting a "ambiguous invocation match" error from he lambda expression below.  Can anyone explain why?</p>
  
  <pre><code>var result = lineStrings
               .Where(a =&gt; lineStrings
               .Count(b =&gt; b.TransitMapSegmentID == a.TransitMapSegmentID) &gt; 1);
  </code></pre>