Do you like the Custom Code functionality in SSRS?
And what would you think if SSIS offered the same possibility? Imagine, being able to write a custom function in .NET and then use it in any expression in your package, how powerful that would be!
There’s already one function I would have written today: GetFilename(string path).
If you believe such functionality to be useful, please vote on the following Connect request: Add user defined function support to the SSIS expression language