“Please close SPWeb objects when you are done with all objects obtained from them, but not before”

DO NOT use SPList directly from methods in webparts & application pages. SPList is a sharepoint object & will instantiate a new SPWeb Object,
if used outside of its parent SPweb object. Always perform operation on SPObjects with in the SPWeb(parent SPObject) context.

or else
We will get the exception with this message : “Please close SPWeb objects when you are done with all objects obtained from them, but not before”

Muchos Muchos Gracias to Jonas for the explanation & pattern in this article 

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Posted in Sharepoint 2010