title: IIF(IsNothing(Fields!field.value), "", Fields!.value.ToString)) generates error
body: <p>SQL Server 2005 reporting services.</p>
  
  <p>I want to using the following in a report text box: </p>
  
  <pre><code>=IIF(IsNothing(Fields!Certification.Value), "", 
      "Certs: " + Fields!Certification.Value.ToString() )
  </code></pre>
  
  <p>But because both sides (T/F) are evaluated, I get an error on the report when the field is null. How can I get around this?</p>