title: Filter result using linq to return a count of entries by remove duplicates using specific parameter
body: <p>For example:</p>
  
  <p>The list is list of Users</p>
  
  <pre><code>First entry: User -&gt; Id=111 name=aaa
  
  First entry: User -&gt; Id=123 name=aaa
  
  First entry: User -&gt; Id=124 name=ccc
  
  First entry: User -&gt; Id=125 name=ddd
  
  First entry: User -&gt; Id=126 name=ddd
  </code></pre>
  
  <p>The result if the param is Id is 5 and if it's name it will be 3 (because there is 3 unique names)</p>
  
  <p>The expected output is the count of Users with provided parameter when this param is distinct.</p>
  
  <p>Thanks in advance</p>