Error codes returned by IIS Admin Base Object are HRESULTs. The errors beginning with MD_ are already HRESULTs, whereas the Win32® errors, beginning with ERROR_, are converted to HRESULTs by the RETURNCODETOHRESULT macro. The conversion adds 80070000 to the Win32 error code. Other COM and RPC HRESULTs can also be returned.
The following error codes are specific to the Metadata Key.
| Error Code | Description |
| MD_ERROR_DATA_NOT_FOUND | The specified data was not found in the metabase. |
| MD_ERROR_INVALID_VERSION | The version specified in metadata storage was not recognized. |
| MD_WARNING_DUP_NAME | A key or data was specified more than once. The duplicate was ignored. |
| MD_WARNING_INVALID_DATA | The specified data is invalid and has been ignored. |
| MD_WARNING_PATH_NOT_FOUND | The specified key path was not found. The key and its associated metadata were ignored. |