How to pass multi-value parameters to a SQL query in SSRS?

In SSRS, allowing users to select multiple options from a parameter drop-down list is a common requirement. How can you properly pass a multi-value parameter into a T-SQL dataset query?

Solution:

When you enable "Allow multiple values" in parameter properties, SSRS passes a comma-separated list of selected values to the underlying dataset.

Use the IN operator inside your SQL query dataset definition:

SELECT 
    ProductID, 
    ProductName, 
    Category 
FROM Sales.Products 
WHERE Category IN (@CategoryList)

SSRS automatically formats the parameter variable @CategoryList so SQL Server can process multiple selected items.