title: Get index of an object in a Generic list
body: <p>I have a list of custom objects with two properties as identifiers (IDa and IDb).</p>
  <p>Every time I remove an object I need to know its index. How do I get an index of an object without looping all the list?</p>
  <pre><code>List&lt;CustomObject&gt; list = new List&lt;CustomObject&gt;();
  list.RemoveAll((MiniMapRecord p) =&gt; p.IDa == IDa.SystemID &amp; p.IDb == pInputRecordMap.IDb);
  </code></pre>