SSRS Expression Field with Multi-value parameter embedded in IIf Statement

Question

I am working on creating an expression to check the value of a parameter and then display a text field based upon the value of the passed in parameter. Here is my current code

=IIf(Parameters!AssessmentType.Count = 3, "All Assessments",
IIf(Parameters!AssessmentType.Count = 2, IIf(Parameters!AssessmentType.Value(0) = 2 AND 
Parameters!AssessmentType.Value(1) = 3, "Initial and Review Assessments", 
IIf(Parameters!AssessmentType.Value(0) = 2 And Parameters!AssessmentType.Value(1) = 4, 
"Initial and Closing Assessments", IIf(Parameters!AssessmentType.Value(0) = 3 
And Parameters!AssessmentType.Value(1) = 4, "Review and Closing Assessments", 
IIf(Parameters!AssessmentType.Value(0) = 3 And 
Parameters!AssessmentType.Value(1) = 2, "Initial and Review Assessments", 
IIf(Parameters!AssessmentType.Value(0) = 4 And Parameters!AssessmentType.Value(1) = 2, 
"Initial and Closing Assessments", IIf(Parameters!AssessmentType.Value(0) = 4 
And Parameters!AssessmentType.Value(1) = 3, "Review and Closing Assessments","")))))), 
IIf(Parameters!AssessmentType.Count = 1, IIf(Parameters!AssessmentType.Value(0) = 2, 
"Initial Assessments", IIf(Parameters!AssessmentType.Value(0) = 3, "Review Assessments", 
IIf(Parameters!AssessmentType.Value(0) = 4, "Closing Assessments", ""))), "")))

The parameter has specified values of 2, 3, and 4. As well as being a multi-valued parameter. The parameter is also involved in a filter expression for the main dataset.

The current expression works for having all three parameter values selected as well as having any two parameter values selected, however, whenever a single parameter value is selected, an undefined error is returned. The expression is sitting in the header of my report and does not allow for any trouble/bug fixing as the error type is not defined.

Any help is always appreciated!!

Answer 1

I ended up just using three different text boxes with visibility expressions to sort out the display. Everything works now.

Answer 2

Assuming that your parameters labels are "Initial", "Review" and "Closing" liek this...

Then you could simply do this...

= IIF(
        Parameters!AssesmentType.Count = 3,
        "All",
        JOIN(Parameters!AssesmentType.Label, " and ") 
    )
    & " Assesments"