using variable in SSIS

Hi,

I have a question in "script task" and "script component".

(1). in "scrip task". I need use "Dts" Variables to access variable like below
 string xls_name = (string)Dts.Variables["User::strFileName"].Value;
but in "script component" I need use "this" to access variable like below
this.Variables.strFileName

I don't understand why it need do like this way, and I would like to learn it. could someone teach me about this.

(2) in  "script component", there are different function block like PreExecute(), postExecute(), CreateNewOutputRows()...etc.

Is it possible to make global variable in one block and let other block can access it. Could you please give me a small code example. thank you

thanks in advance