asp.net - 'newwcf.Client' does not contain a definition for 'Where' -

hi have following code: 

but m getting error 'newwcf.client' not contain definition 'where'
please help..

using system; using system.collections.generic; using system.linq; using system.runtime.serialization; using system.servicemodel; using system.text; using system.data;  namespace newwcf {     public class myservice : imyservice      {       public  list<clientdetails> getclient()         {             list<clientdetails> client = new list<clientdetails>();             var sql = client.where(cn => cn.clientname).tolist();  //getting error here             return sql;          }      } } 

c# case sensitive...should try

var sql = client.where(cn => cn.clientname).tolist();