CWbemProviderGlue::GetAllDerivedInstancesAsynch method (wbemglue.h)

[The CWbemProviderGlue class is part of the WMI Provider Framework which is now considered in final state, and no further development, enhancements, or updates will be available for non-security related issues affecting these libraries. The MI APIs should be used for all new development.]

The GetAllDerivedInstancesAsynch method retrieves a list of instances supported by a particular provider and derived from a particular base class. This method allows the provider to respond asynchronously by returning one instance at a time.

Syntax

HRESULT GetAllDerivedInstancesAsynch(
  LPCWSTR                    pszBaseClassName,
  Provider                   *pRequester,
  LPProviderInstanceCallback pCallback,
  LPCWSTR                    pszNamespace,
  MethodContext              *pMethodContext,
  void                       *pUserData
);

Parameters

pszBaseClassName

Name of base class for which the list should be returned.

pRequester

Pointer for the callback function pointed to by pCallback.

pCallback

Pointer to a static function with this prototype.

  static HRESULT WINAPI Classname::FunctionName(
     Provider *pProvider,
     CInstance *pInstance,
     MethodContext *pMethodContext,
     void *pUserData );

where Classname is the name of a class derived from class Provider. It is an instance of this class that is the "this" pointer defined by pRequester. This function is called to return each instance supported by the provider specified by pszClassName.

pszNamespace

Namespace of the class name specified by pszClassName. When this parameter is NULL, the default namespace root\cimv2 is used.

pMethodContext

Pointer to the current context. A context must be provided to prevent deadlocks. Either use the context passed into the provider by Provider::EnumerateInstances or Provider::ExecQuery, or else obtain it from the instance using CInstance::GetMethodContext. This parameter must not be NULL.

pUserData

Pointer to user-defined data that is passed to the function pointed to by pCallback.

Return value

The method returns WBEM_S_NO_ERROR if the operation was successful, WBEM_E_OUT_OF_MEMORY if the operation failed due to lack of memory, or any other HRESULT error code.

Remarks

The GetAllDerivedInstancesAsynch method performs almost the same function as GetAllDerivedInstances. However, instead of returning one arbitrarily large array of instances, the provider passes an instance to the function specified by pCallBack each time the instance is retrieved from a provider. This allows the provider to use less memory, and to begin returning instances to the client sooner.

This method is semantically equivalent to the query SELECT * FROM pszBaseClassName.

Because the call-back to the sink might not be returned at the same authentication level as the client requires, it is recommended that you use semisynchronous communication instead of asynchronous. If, however, you require asynchronous communication, see Calling a Method.

For more information about using methods semisynchronously, see CWbemProviderGlue::GetAllDerivedInstances and Calling a Method.

Requirements