title: c# Linq Oracle convert long to string for join
body: <p>I'm having the following issue, in trying to join up two tables in Oracle.
  One of the tables has a string value and the other is a long.</p>
  
  <pre><code>var query = (from d in context.entity
  join m in context.entity2
  on d.ordernum.Substring(2) equals m.ordernum.ToString())
  select new { d.ordernum, d.customer, m.recordkey});
  var items = query.ToList();
  </code></pre>
  
  <p>The issue is that this does not work with Oracle</p>
  
  <ol>
  <li><p>Cant use SQLFunctions as this is an Oracle Database</p></li>
  <li><p>Cant use .ToString()</p>
  
  <p>LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method cannot be translated into a store expression.</p></li>
  <li><p>Cast use long.Parse()</p>
  
  <p>LINQ to Entities does not recognize the method 'Int64 Parse(System.String)' method, and this method cannot be translated into a store expression.</p></li>
  </ol>
  
  <p>Any helps would be appreciated.</p>