Откройте папку и выделите определенный файл с помощью WPF

Аргументы командной строки Explorer
http://support.microsoft.com/kb/152457

Explorer [/n] [/e] [(,)/root,<object>] [/select,<object>]

/n                Opens a new single-pane window for the default
                  selection. This is usually the root of the drive Windows
                  is installed on. If the window is already open, a
                  duplicate opens.

/e                Opens Windows Explorer in its default view.

/root,<object>    Opens a window view of the specified object.

/select,<object>  Opens a window view with the specified folder, file or
                  application selected.

Вы также захотите поставить цитаты вокруг имени файла так:

startInfo.FileName = "explorer.exe";
startInfo.Arguments = "/select,\"" + ConfigFile.File.FullName + "\"";