Files to look at:

GridView - How to open popup on a hyperlink click

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This example contains a Customers grid with a hyperlink column. When a hyperlink is clicked, a popup window is opened to display detail data - orders - of a given customer. Orders is the GridView extension in the content of the PopupControl.

See also:
How to display detail data within a popup window using ContentUrl (MVC)
How to display detail data within a popup window