SSRS Multi-Value Blank

Question

I have a SSRS report with a few dropdowns that are chained together. Basically a item is selected from dropdown 1 which then populates dropdown 2 and so on. The issue I am having is that in dropdown 3, which is a multi-value populated from a query I want to allow no selection.

Problem #1
Although that report parameter is set to allow blanks, it will not let me deselect all values. I get a required error.

Problem #2
In my stored procedure I have the parameter in question being filtered by an IN statement, which will not work if a blank is coming though as I want the blank to skip that filter.

Problem #3
The dropdown #3 may not have any values once the other 2 are selected.

I feel that I am using the multi-value incorrectly causing all 3 issues. Any help is appreciated.

Answer 1

Problem #1

Can you add something like this to the end of your query that populates the DropDown?

Union
Select Null as (value field name), 'None' as (label field name)

Problem #2

Do you have to pass in an empty value? Can you do something like this:

WHERE (@Param is null OR t.id in @Param)

or even

WHERE (@Param ='' OR t.id in @Param)

If you want to keep it as a string?

Problem #3

Should be taken care of if you can do my suggestions for 1 and 2.