Microsoft says that you cannot allow multiple values for a parameter in Report Builder 2.0 when using stored procedures. https://technet.microsoft.com/en-us/library/Dd207127(v=SQL.100).aspx
I cannot find a similar statement for Report Builder 3.0. How does report builder send the data contained in a parameter with multiple selections to a stored procedure? It seems from this post that it passes them as a string, is that right? https://www.mssqltips.com/sqlservertip/2844/working-with-multiselect-parameters-for-ssrs-reports/
This seems way too complicated of a method to unparse the string sent by Report Builder to the database.
It seems that tables can be passed as parameters into stored procedure in SQL Server 2008: How to pass an array into a SQL Server stored procedure Is there a way to pass a table from Report Builder 3.0 to SQL Server 2008?