In any text editor, you can easily delete all search matches by running a search-and-replace with a blank replacement text. Deleting all lines without search matches is often much more difficult. Not so in EditPad Pro 7.
In EditPad Pro 7, simply select Search|Search Options|Inverted Line by Line in the menu to turn on the “inverted line by line” search option. The Invert button on the Search toolbar does the same. This option tells EditPad Pro 7 to find all lines that do not contain the search term. If you turn it on and run a search-and-replace with a blank replacement text, all lines that do not contain the search term will be deleted, keeping only lines with search matches
If you want to do the opposite, keeping only lines without search matches, turn on Search|Search Options|Line by Line and make sure Search|Search Options|Inverted Line by Line is off. If you use the Search toolbar, make sure the Line button is pushed down and the Invert button is not. Then search-and-replace with a blank replacement text to remove all lines with search matches, keeping only lines without search matches.
Doing line-based searches does impose one limitation. Normally, EditPad Pro allows search matches to span any number of lines. When the “line by line” option is turned on, EditPad Pro searches through each line separately and thus cannot find matches that span multiple lines. This limitation can be a benefit if you want to restrict regular expression matches to single lines, without having to edit your regular expression.