OFN_NOVALIDATE top-level constant Null safety
The common dialog boxes allow invalid characters in the returned file name. Typically, the calling application uses a hook procedure that checks the file name by using the FILEOKSTRING message. If the text box in the edit control is empty or contains nothing but spaces, the lists of files and directories are updated. If the text box in the edit control contains anything else, nFileOffset and nFileExtension are set to values generated by parsing the text. No default extension is added to the text, nor is text copied to the buffer specified by lpstrFileTitle. If the value specified by nFileOffset is less than zero, the file name is invalid. Otherwise, the file name is valid, and nFileExtension and nFileOffset can be used as if the OFN_NOVALIDATE flag had not been specified.
const OFN_NOVALIDATE = 0x00000100;