title: Custom .ToString() Formats in .rdlc Reports
body: <p>I have a custom business object which overloads the .ToString() function. It also implements IFormattable.ToString, so I can define my own custom formats.</p>
  
  <p>This approach seems to work everywhere in my app, except .rdlc reports. For example, I have a text field on a report with the following expression:</p>
  
  <pre><code>=Fields!MyField.Value.ToString("lr")
  </code></pre>
  
  <p>"lr" is a custom format I have created. When running the report I always get #Error as the output. I've placed breakpoints in my .ToString function and stepped through the code as the report is running, and I know the function is returning the correct value, but the report just doesn't seem to be capable of receiving and displaying it.</p>