Reporting Services Expression

I'm trying to set the Hidden-property of a Textbox based on this expression:

=IIf(IsNothing(Parameters!customer_numbers.Value) AND 
     IsNothing(Parameters!country_codes.Value),False,True)

Error: "Argument not specified for parameter 'Fa开发者_如何学ClsePart' of Public Function IIf(Expression As Boolean, TruePart As Object, FalsePart As Object) As Object"

I'm a jScript/C# guy and not used to this pseudo-VB language. What is wrong?

Regards Alex

My answer is that nothing is wrong!

I just created a test report (RS 2008) with your two parameters: customer_numbers and country_codes. I set the parameters to be text fields and nullable.

I added a textbox with the text "Both parameters are null". I set the visibility expression via copy and paste from your question.

The report starts fine, and if I set both parameters to be null then I see the textbox. The rdl of the textbox turns out like this:

 <Visibility>
      <Hidden>=IIf(IsNothing(Parameters!customer_numbers.Value) AND 
 IsNothing(Parameters!country_codes.Value),False,True)</Hidden>
    </Visibility>