SSIS 2012 Foreach Loop w/file parameter fails

I've used Foreach Loop Containers in many SSIS 2008 packages for data flow tasks that import data from flat files with names that change daily (the name has a datestamp). I create the file name with a wild card (file_name_*.csv), add a variable for the file, and associate that variable with the File Connection by adding a ConnectionSting expression that references the file variable in the Foreach Loop. I've tried to do the same thing in SSIS 2012 and keep getting a failure saying "Cannot open the datafile file_name_yymmdd.csv" I know that file can be accessed, because if I run it as a simple data flow using the exact file name and no variable/expression, it works fine. Is there something in SSIS 2012 that has changed in this routine that I am unaware of? Do I need to configure the variable and connection string expression differently? Thanks JDC