FileUpload

Question

hello my firends
I have a web project that have many forms.Most of the forms  have to have fileUploading and resizing picure file ability.So I have decided to write a class that have a method for resize and file upload .but I can't use HttpContext.current.Server.Mappath() in my class although  this method works well in code_behind .
please tell me how can i use server.Mappath in my class.
tnx a lot.