OFN_FILEMUSTEXIST top-level constant Null safety
The user can type only names of existing files in the File Name entry field. If this flag is specified and the user enters an invalid name, the dialog box procedure displays a warning in a message box. If this flag is specified, the OFN_PATHMUSTEXIST flag is also used. This flag can be used in an Open dialog box. It cannot be used with a Save As dialog box.
const OFN_FILEMUSTEXIST = 0x00001000;