Parameters: How to set null value

Hi, I have a problem.
I have two parameters: Group and Selection

In the first I have 2 choices: Total and Day
And the value of the second parameter is dynamic and is sets to allow null value
The behaviour I want is this: If a user select Total in the first parameter, the second must be set to NULL, if the selection is Day, the second must be set with a data set.

How I can set the value of the second parameter with null, I tryed

Have anyone an idea?

One way I have done this in the past is using '-1' as the Total value, and then letting the stored procedure pass in a null value by setting all '-1' parameters to null.

if @.param1 = '-1' set @.param1=null

System.DbNull.Value may work too.

Yet another option that may be possible is to use an expression to convert the parameter to a null value, and pass in the expression instead of the parameter to the report.

cheers,

Andrew

|||thanks,
I tryed System.DbNull.Value but give me this error : DbNull is a type in system and cannot be used as an expression

Perhaps I wrong something:
I wrote this in the datasets I use for the second parameter

=iif(Parameters!parm1.Value = 2,
"select a11.DATE_ID from Day" ,System.DBNull )

Another question, where I have to place this expression, in the store procedure?

if @.param1 = '-1' set @.param1=null

but I use a dataset.

Thanks in advance

|||

Not sure exactly how you are passing in a dataset as a parameter but looks interesting.

Instead of null perhaps you could use "SELECT null as DateID" instead? Or maybe an empty string?

The syntax for getting dbnull is to use System.DBNull.Value

=iif(Parameters!parm1.Value = 2,
"select a11.DATE_ID from Day" ,System.DBNull.Value )

cheers,

Andrew

|||If I use this expression "System.DBNull.Value" something don't work but I don't understand what.
but following your example and this link forums.microsoft.com/MSDN/ShowPost.aspx?PostID=766574&SiteID=1
it works

thanks