IWbemHiPerfProvider::CreateRefreshableEnum method (wbemprov.h)

The IWbemHiPerfProvider::CreateRefreshableEnum method creates a new refreshable enumeration. The WMI Refresher calls this method in response to a client request to IWbemConfigureRefresher::AddEnum. The provider associates the supplied IWbemHiPerfEnum object with the supplied refresher. On each call to the supplied refresher's Refresh method, the provider ensures that the enumerator contains a set of all the instances of the class listed in the wszClass parameter and that these instances contain updated information. One possible way to do this would be to keep an array of refreshable enumerators in the refresher.

Syntax

HRESULT CreateRefreshableEnum(
  [in]  IWbemServices   *pNamespace,
  [in]  LPCWSTR         wszClass,
  [in]  IWbemRefresher  *pRefresher,
  [in]  long            lFlags,
  [in]  IWbemContext    *pContext,
  [in]  IWbemHiPerfEnum *pHiPerfEnum,
  [out] long            *plId
);

Parameters

[in] pNamespace

An IWbemServices pointer back into Windows Management, which can service any requests made by the provider. If pNamespace must call back into Windows Management during its execution, the provider calls AddRef on this pointer.

[in] wszClass

Constant, null-terminated string of 16-bit, Unicode characters that contains the name of the class, whose instances are refreshed in the pHiPerfEnum parameter.

[in] pRefresher

Pointer to a IWbemRefresher object that contains a refresher obtained by calling IWbemHiPerfProvider::CreateRefresher.

[in] lFlags

Reserved. This parameter must be 0 (zero).

[in] pContext

Typically NULL; otherwise, a pointer to an IWbemContext object required by one or more dynamic class providers. The values in the context object must be specified in the specific provider's documentation. For more information about this parameter, see Making Calls to WMI.

[in] pHiPerfEnum

Pointer to a IWbemHiPerfEnum object that contains the high-performance enumeration.

[out] plId

Pointer to an integer returned by the provider that uniquely identifies the refreshable enumeration.

Return value

This method returns an HRESULT that indicates the status of the method call. The following list lists the value contained within an HRESULT.

Remarks

The provider must not modify the refreshable enumerator except during a refresh operation. The enumeration is shallow, so all instances placed in the enumerator should be of the class specified by wszClass.

The provider must not access the enumerator unless WMI calls the IWbemRefresher::Refresh method of the owner. As with refreshable objects, the provider must not update the enumerator unless the object owning the enumerator refreshes the enumerator.

Examples

The following code example describes how to implement CreateRefreshableEnum.

HRESULT CHiPerfProvider::CreateRefreshableEnum(
  /* [in] */IWbemServices *pNamespace,
  /* [in] */LPCWSTR wszClass,
  /* [in] */IWbemRefresher *pRefresher,
  /* [in] */long lFlags,
  /* [in] */IWbemContext *pCtx,
  /* [in] */IWbemHiPerfEnum *pEnum,
  /* [out] */ long *plId
)
{
  // Use a private interface defined
  // to talk with the refresher.
  IMyRefresher* pMyRefr = NULL;

  HRESULT hres = pRefresher->QueryInterface(
    IID_IMyRefresher,
    (void**) &pMyRefr );

  if ( SUCCEEDED( hres ) )
  {
  LPLONG plLastId;
    // Generates a unique identifier
    *plId = InterlockedIncrement( &plLastId );

    // Use an internal method to add the
    // enumerator to an array.
    pMyRefr->AddEnum( wszClass, *plId, pEnum );

    pMyRefr->Release();
  }

  return hres;
}

Requirements

See also

Developing a WMI Provider

IWbemHiPerfProvider

Making an Instance Provider into a High-Performance Provider

Performance Counter Provider

Writing an Instance Provider