IFunctionInstanceCollectionQuery::Execute method

[Function Discovery is available for use in the operating systems specified in the Requirements section. It may be altered or unavailable in subsequent versions.]

Performs the query defined by IFunctionDiscovery::CreateInstanceCollectionQuery.

Syntax

HRESULT Execute(
  IFunctionInstanceCollection **ppIFunctionInstanceCollection
);

Parameters

ppIFunctionInstanceCollection

A pointer to an IFunctionInstanceCollection interface pointer that receives the requested function instance collection.

Return Value

Possible return values include, but are not limited to, the following.

Return code Description
S_OK
The method completed successfully. Results are returned synchronously in ppIFunctonInstanceCollecton.
E_OUTOFMEMORY
The method is unable to allocate the memory required to perform this operation.
E_PENDING
Some of the results will be returned by asynchronous notification. See the remarks for details.
 

A predefined query is a query of a layered category. When a predefined query is executed, each provider that returns a function instance also returns an HRESULT value. The provider HRESULT values are aggregated, and the value returned by the Execute method reflects these aggregate results. Results are aggregated as follows:

  • If all providers return S_OK, Execute returns S_OK.
  • If at least one provider returns E_PENDING, and all other providers return either S_OK or E_PENDING, Execute returns E_PENDING.
  • If all providers return an error value (that is, a value other than S_OK or E_PENDING), Execute returns the error value returned by the network provider that was last queried. Also, if the client's IFunctionDiscoveryNotification callback routine was provided to IFunctionDiscovery::CreateInstanceCollectionQuery, an OnError notification is sent for each provider. Each OnError notification contains the HRESULT returned by the provider.
  • If at least one provider returns an error value, and all other providers return S_OK, Execute returns S_OK. OnError notifications are sent as described above.
  • If at least one provider returns an error value, and at least one provider returns E_PENDING, Execute returns E_PENDING. OnError notifications are sent as described above.
When Execute returns S_OK, ppIFunctionInstanceCollection contains the results of the query. If an IFunctionDiscoveryNotification interface is provided to the CreateInstanceCollectionQuery method of IFunctionDiscovery, then changes to the results will be communicated using that interface.

When Execute returns E_PENDING, the result set will be returned asynchronously through the IFunctionDiscoveryNotification interface provided to the CreateInstanceCollectionQuery method of IFunctionDiscovery. ppIFunctionInstanceCollection may be NULL or may contain a partial result set. The enumeration is complete once the OnEvent method of IFunctionDiscoveryNotification is called with FD_EVENTID_SEARCHCOMPLETE. After the FD_EVENTID_SEARCHCOMPLETE event is received, additional notifications are updates to the results.

Remarks

This method must be must be invoked by the client program before any data can be retrieved from the query object. When called, this method performs the following:

  1. Retrieves the function instance collection object.
  2. Queries the provider of the category that is passed into IFunctionDiscovery::CreateInstanceCollectionQuery.
  3. Retrieves the category provider.
  4. Queries the category provider using the subcategory data to generate the collection using query constraints.
  5. Initiates the update notification mechanism if the address of the client program's IFunctionDiscoveryNotification callback routine is provided to IFunctionDiscovery::CreateInstanceCollectionQuery.
  6. Caches the collection data and returns.
Function Discovery network providers only return function instances through the IFunctionDiscoveryNotification interface. They return no function instances directly when this method is invoked. Instead, Execute simply initiates an entirely asynchronous retrieval operation and returns E_PENDING to indicate that the results will be returned asynchronously. Notifications must be used to retrieve function instances from Function Discovery network providers.

Requirements

   
Minimum supported client Windows Vista [desktop apps only]
Minimum supported server Windows Server 2008 [desktop apps only]
Target Platform Windows
Header functiondiscoveryapi.h
DLL FunDisc.dll

See Also

Function Discovery Queries

IFunctionInstanceCollectionQuery