title: Adding new object to List is not working
body: <p>I'm trying to add a new <code>OldFlatFile</code> to <code>OldFlatFileList</code> which works but not on adding new one. I can not see error and I don't know if there's something wrong with the code below?  </p>
  
  <p><code>OldFlatFileList</code> count is same as before and after adding:</p>
  
  <pre><code>    var selectedPackage = FlatFileHelper.GetSelectedPackage(OldFlatFileList);
      var primaryFeature = new PrimaryFeatures(){ DataTypeCode = "abc" };
  
      OldFlatFileList.ToList().Add(
      new OldFlatFile
      {
          new OldFlatFileEntry
          {
              InformationFields = selectedPackage.InformationFields,
              PrimaryFeatures = primaryFeature,
              SecondaryFeatures = null
          }
      });
  </code></pre>
  
  <hr>
  
  <pre><code>    private IEnumerable&lt;OldFlatFile&gt; OldFlatFileList
      {
          get { return Session[SystemConstant.OldFlatFileListKey] as List&lt;OldFlatFile&gt;; }
          set { Session[SystemConstant.OldFlatFileListKey] = value; }
      }
  </code></pre>
  
  <hr>
  
  <pre><code>    public class OldFlatFile : List&lt;OldFlatFileEntry&gt;
      {}
  </code></pre>