get value from xml using Xelement

I am trying to get the value of the attribute "Id" inside the entity element from the class with the name of "ECMInstruction" but nothing is returned.

    <?xml version="1.0" encoding="utf-8"?>
    <Root>
      <Class Name="ECMInstruction" Style="Top">
        <Entity Id="1" Name="DocumentInformation" />
      </Class>
      <Class Name="dfgfggfdg" Style="Top">
        <Entity Id="1" Name="dfgfgfdgd" />
      </Class>
    </Root>

  private void dcLisT_SelectedIndexChanged(object sender, EventArgs e)
    {
       String curItem = dcList.SelectedItem.ToString();

       IEnumerable<String> lList =
         from el in doc.Descendants("Entity")
         where el.ElementsBeforeSelf("Class") && Attribute("Name").Value == curItem
         select (String)el.Attribute("Id").Value;

       EntityList.Items.AddRange(lList.ToArray());
    }