SSRS Report giving error for Join expression

Question

I have declared a multi value parameter in my SSRS report. The parameter is a Date and it has multiple values like:

06/01/2021
05/01/2021
04/01/2021

Now when I select date as 06/01/2021, 05/01/2021 then the expression should show as Reportname_ with previous months first and last dates. Example: if I select date as

06/01/2021
05/01/2021
04/01/2021

then result should be

Reportname_05/01/2021-05/31/2021_04/01/2021-04/30/2021_03/01/2021-03/31/2021

I tried with Join but getting error. The expression I am using is

Join(dateadd(“m”,-1,dateserial(year(Parameters!date.Value(0)), month(Parameters!date.Value(0)), 1)) & 
"-" & 
dateadd(“m”,0,dateserial(year(Parameters!date.Value(0)), month(Parameters!date.Value(0)), 0)), "_")

Answer 1

You have to use custom code to parse your parameter and create the string expression

Add the following custom code to your report

Public Function ParseDate(ByVal parameter as Parameter) as String

Dim s as String 
Dim seperator as String 
Dim dt as Date

    For i as integer = 0 to parameter.Count-1
     dt = DateSerial(Year(parameter.Value(i)), Month(parameter.Value(i)), 1)
      s = s + seperator + Format(DateAdd("m",-1,dt),"MM/dd/yyyy") + "-" + Format(DateAdd("d",-1, dt),"MM/dd/yyyy") 
      seperator = "_"

    Next
 
   Return s
End Function

For your textbox returning the report name and date values use the following expression

=Globals!ReportName & "_" & Code.ParseDate(Parameters!Date)