title: How to filter by postal code range?
body: <p>I have to do an <code>ExecuteMultiple</code>, using a filter on the system-field <code>address1_postalcode</code>.</p>
  
  <p>The condition of the filter is that the postal code should be in a range.</p>
  
  <p>I used these two filters, but the result doesn't take into account the condition:</p>
  
  <pre><code>filter.Conditions.Add(
    new ConditionExpression(
      "address1_postalcode", 
      ConditionOperator.LessThan, 
      postalcodeMax
    )
  );
  
  filter.Conditions.Add(
    new ConditionExpression(
      "address1_postalcode", 
      ConditionOperator.GreaterThan, 
      postalcodeMin
    )
  );
  </code></pre>
  
  <p><code>postalcodeMin</code> and <code>postalcodeMax</code> are integers, and I know that <code>postalCode</code> field is string.</p>
  
  <p>Do you have any idea?</p>