Default Directory For Common Dialog - social.msdn.microsoft.com

If lpstrFile contains a path, that path is the initial directory. Otherwise, lpstrInitialDir specifies the initial directory. Otherwise, if the application has used an Open or Save As dialog box in the past, the path most recently used is selected as the initial directory. However, if an application is not run for a long time, its saved selected path is discarded. If lpstrInitialDir is NULL ...

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