get data flow task 's system::sourceid with c# code

I use c# code to do something about the package, when I dipose one event handler, we can use the sourceid system variable, but can we get this value when c# code, or we can see this in task property window?

what I want to do is capture the rowcount info, I do this in event handler, but I can not distinguish which the source is what I want, could you tell me ,thanks in advance.

such as:

@[System::SourceID]=="{0559251C-A429-4047-8390-8AAC61E03606}" 

I want to use like this expression to filter then do something ,such as insert the rows to db tables

yaoyao