The error message is saying "The DataView constructor does not have an overloaded version which accepts a single parameter which is a GridView class instance"
It has overloads which accept no parameters, a DataTable, or a DataTable and some filter info:
DataView Class (System.Data)[
^] but it can't accept a GridView.
Probably, you want to pass the DataTable
dt
, but it's your app, not mine and I can't be sure.