passing textbox value to a class file in App_code ??

Hey There:)
I would like to know if someone can help me please
I have a class1.vb file in App_code
I have a aspx page called test1.aspx  and on the page I have  textbox1 control
how can I from inside the class1.vb file get the textbox1 control value that in test1.aspx
or another way to ask........ how can I pass the textbox1 value to class1.vb??
Thank you for your help I really appreciate this a lot:)
Regards
Jake
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