nMaxFile
Specifies the size, in TCHARs, of the buffer pointed to by lpstrFile. For the ANSI version, this is the number of bytes; for the Unicode version, this is the number of characters. The buffer must be large enough to store the path and file name string or strings, including the terminating NULL character. The GetOpenFileName and GetSaveFileName functions return FALSE if the buffer is too small to contain the file information. The buffer should be at least 256 characters long.