'T' does not contain a definition
<p>Is it possible to do the following (If so I can't seem to get it working.. forgoing constraints for the moment)...</p>

<p>If the type (because it's ommitted) is inferred, what's the problem?</p>

<pre><code>private void GetGenericTableContent&lt;T&gt;(ref StringBuilder outputTableContent, T item)
{
    outputTableContent.Append("&lt;td&gt;" + item.SpreadsheetLineNumbers + "&lt;/td&gt;");
}

// 'item' is either DuplicateSpreadsheetRowModel class or SpreadsheetRowModel class
</code></pre>

<p>With the above code I get the following error:</p>

<blockquote>
  <p>'T' does not contain a definition for 'SpreadsheetLineNumbers' and no extension method 'SpreadsheetLineNumbers' accepting a first argument of type 'T' could be found (are you missing a using directive or an assembly reference?)</p>
</blockquote>