If you are certain the files are correct but the error persists, you may need to re-register the library in Windows.
Note: If this fails, the DLL version you have is likely incompatible with your current Windows OS build or system architecture (x86 vs x64). hcnetsdk.dll 9 hikvision error
NET_DVR_USER_LOGIN_INFO loginInfo = 0;
loginInfo.dwSize = sizeof(NET_DVR_USER_LOGIN_INFO);
// Check IP string is valid, port >0, user/pass not empty
Functions like NET_DVR_RealPlay_V40 require that the struPlayInfo structure’s dwSize member equals sizeof(NET_DVR_PREVIEWINFO). Forgetting this leads to error 9. If you are certain the files are correct