Your C# skills could do with some work! 🙂

Try this:

public void Main()
{
string networkPath = Dts.Variables["User::FileDestinationPath"].Value;
string[] filePaths = Directory.GetFiles(networkPath , "*.csv", System.IO.SearchOption.AllDirectories);
foreach...

For those who would like to try for themselves, a Regex tester can be found here. It suggests that Frederico's concern is not an issue, because I tested...

SQL Prompt has some very useful options for handling brackets (remove them unless doing so causes an issue) and aliasing: