How do you submit a List of items to a Stored Procedure to limit results?
If you are using SQL 2008 or higher you can use a table valued parameter which would allow you to pass in what is basically an array from the .NET side then use the table variable as an in clause an Nick has said.

If you aren't using SQL 2008 or higher then you'll want to pass in the values as an XML document, then use xquery or OPENXML to parse the XML document and put the values into a temp table (or table variable depending on how many values you expect).  Then use the temp table as part of an IN within the WHERE clause.