ExecNotificationQueryWmi function

Article
09/15/2021

Executes a query to receive events. The call returns immediately, and the caller can poll the returned enumerator for events as they arrive. Releasing the returned enumerator cancels the query.

Note

This API is for internal use only. It's not intended for use from developer code.

Syntax

HRESULT ExecNotificationQueryWmi (
   [in] BSTR                    strQueryLanguage,
   [in] BSTR                    strQuery,
   [in] long                    lFlags,
   [in] IWbemContext*           pCtx,
   [out] IEnumWbemClassObject** ppEnum,
   [in] DWORD                   authLevel,
   [in] DWORD                   impLevel,
   [in] IWbemServices*          pCurrentNamespace,
   [in] BSTR                    strUser,
   [in] BSTR                    strPassword,
   [in] BSTR                    strAuthority
);

Parameters

strQueryLanguage
[in] A string with the valid query language supported by Windows Management. It must be "WQL", the acronym for WMI Query Language.

strQuery
[in] The text of the query. This parameter cannot be null.

lFlags
[in] A combination of the following two flags that affect the behavior of this function. These values are defined in the WbemCli.h header file, or you can define them as constants in your code.

Constant	Value	Description
`WBEM_FLAG_RETURN_IMMEDIATELY`	0x10	The flag causes a semisynchronous call. If this flag is not set, the call fails. This is because events are received continuously, which means the user must poll the returned enumerator. Blocking this call indefinitely makes that impossible.
`WBEM_FLAG_FORWARD_ONLY`	0x20	The function returns a forward-only enumerator. Typically, forward-only enumerators are faster and use less memory than conventional enumerators, but they do not allow calls to Clone.

pCtx
[in] Typically, this value is null. Otherwise, it is a pointer to an IWbemContext instance that can be used by the provider that is providing the requested events.

ppEnum
[out] If no error occurs, receives the pointer to the enumerator that allows the caller to retrieve the instances in the query's result set. See the Remarks section for more information.

authLevel
[in] The authorization level.

impLevel
[in] The impersonation level.

pCurrentNamespace
[in] A pointer to an IWbemServices object that represents the current namespace.

strUser
[in] The user name. See the ConnectServerWmi function for more information.

strPassword
[in] The password. See the ConnectServerWmi function for more information.

strAuthority
[in] The domain name of the user. See the ConnectServerWmi function for more information.

Return value

The following values returned by this function are defined in the WbemCli.h header file, or you can define them as constants in your code:

Constant	Value	Description
`WBEM_E_ACCESS_DENIED`	0x80041003	The user does not have permission to view one or more of the classes that the function can return.
`WBEM_E_FAILED`	0x80041001	An unspecified error has occurred.
`WBEM_E_INVALID_PARAMETER`	0x80041008	A parameter is not valid.
`WBEM_E_INVALID_CLASS`	0x80041010	The query specifies a class that does not exist.
`WBEMESS_E_REGISTRATION_TOO_PRECISE`	0x80042002	Too much precision in delivery of events has been requested. A larger polling tolerance must be specified.
`WBEMESS_E_REGISTRATION_TOO_BROAD`	0x80042001	The query requests more information than Windows Management can provide. This `HRESULT` is returned when an event query results in a request to poll all objects in a namespace.
`WBEM_E_INVALID_QUERY`	0x80041017	The query had a syntax error.
`WBEM_E_INVALID_QUERY_TYPE`	0x80041018	The requested query language is not supported.
`WBEM_E_QUOTA_VIOLATION`	0x8004106c	The query is too complex.
`WBEM_E_OUT_OF_MEMORY`	0x80041006	Not enough memory is available to complete the operation.
`WBEM_E_SHUTTING_DOWN`	0x80041033	WMI was probably stopped and restarting. Call ConnectServerWmi again.
`WBEM_E_TRANSPORT_FAILURE`	0x80041015	The remote procedure call (RPC) link between the current process and WMI has failed.
`WBEM_E_UNPARSABLE_QUERY`	0x80041058	The query cannot be parsed.
`WBEM_S_NO_ERROR`	0	The function call was successful.

Remarks

This function wraps a call to the IWbemServices::ExecNotificationQuery method.

After the function returns, the caller periodically passes the returned ppEnum object to the Next function to see if any events are available.

There are limits to the number of AND and OR keywords that can be used in WQL queries. Large numbers of WQL keywords used in a complex query can cause WMI to return the WBEM_E_QUOTA_VIOLATION (or 0x8004106c) error code as an HRESULT value. The limit of WQL keywords depends on how complex the query is.

If the function call fails, you can obtain additional error information by calling the GetErrorInfo function.

Requirements

Platforms: See System Requirements.

Header: WMINet_Utils.idl

.NET Framework Versions: Available since 4.7.2

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