XML SelectNodes

I try retrive specific XML node a get child value:

XML:

    <Brands>
         <Brand brand_name="Brioni">
                 <Season season_name = "AI_2015">
                     <Collection collection_name = "Pippo">
                             <Model model_name = "Abito_01">
                                     <ConfigName>Config_01</ConfigName>
                                     <ConfigName>Config_02</ConfigName>
                             </Model>    
                             <Model model_name = "Abito_02">
                                     <ConfigName>Config_03</ConfigName>
                                     <ConfigName>Config_04</ConfigName>
                             </Model>        
                     </Collection>                
                 </Season>
         </Brand>
     </Brands>

And the code:

  XmlDocument doc = new XmlDocument ();
     doc.LoadXml (myXmlString.ToString ());
         
     XmlNodeList modellist;
     XmlNode root = doc.DocumentElement;
         
     modellist =root.SelectNodes("//Brand[@brand_name='Brioni']/Season[@season_name='AI_2015']/Collection[@collection_name='Pippo']");
         
     foreach (XmlNode elem in modellist){   
     Debug.log (elem.Attributes ["model_name"].Value);
     } 

Doesn't work... Somebody can help me?