Visibility controlled by parameter value

I try to put this expression but it comes out error: Before I input the hidden expression, the report works fine.

=iif((Parameters!policy.Value)='2005',true,false)

error msg:

1. The hidden expression for the textbox contains an error: [BC30201] Expression expected
2. The value expression for the textbox contains en error: Input string was not in a correct format

please help

Place this at the textbox properties (Visibility -> Hidden and select Expression)

=iif(Parameters!policy.Value="2005", true, false)


On the textbox itself, right click Expression and place this in:

=Parameters!policy.Value


you can then test it out.
In this case, if you enter 2005 on the Policy parameter, the textbox will be hidden, else will show.

Thanks!