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IMultiInterfaceEventControl::GetSubscriptions method (eventsys.h)

  • Article

Retrieves the collection of subscription objects associated with an event method.

Syntax

HRESULT GetSubscriptions(
  [in]          REFIID                 eventIID,
  [in]          BSTR                   bstrMethodName,
  [in]          BSTR                   optionalCriteria,
  [in]          int                    *optionalErrorIndex,
  [out, retval] IEventObjectCollection **ppCollection
);

Parameters

[in] eventIID

The interface identifier of the firing interface.

[in] bstrMethodName

The event method associated with the subscription collection.

[in] optionalCriteria

A string specifying the query criteria. If this parameter is NULL, the default query specified by the SetDefaultQuery method is used. For details on forming a valid expression for this parameter, see the Remarks section below.

[in] optionalErrorIndex

The location, expressed as an offset, of an error in the optionalCriteria parameter. This parameter cannot be NULL.

[out, retval] ppCollection

The address of a pointer to an IEventObjectCollection interface on a collection object that enumerates the subscriptions associated with the event object.

Return value

This method can return the standard return values E_INVALIDARG, E_OUTOFMEMORY, E_UNEXPECTED, and E_FAIL, as well as the following values.

Return code Description
S_OK
 The method completed successfully.
EVENT_E_QUERYSYNTAX
 A syntax error occurred while trying to evaluate a query string.
EVENT_E_QUERYFIELD
 An invalid field name was used in a query string.
EVENT_E_INTERNALEXCEPTION
 An unexpected exception was raised.
EVENT_E_INTERNALERROR
 An unexpected internal error was detected.

Remarks

This method is a more specialized form of the IEventSystem::Query method. In addition to obtaining only subscription objects, a collection obtained by calling GetSubscriptions is automatically updated whenever the subscription collection changes.

The query criteria specified by the optionalCriteria parameter can be "ALL", to specify a request for all subscription objects, or a Boolean expression denoting one or more conditions a subscription object must meet to be included in the query result. Valid expressions are of the following form:

[NOT] propertynamerelationalOperatorvalue. Valid relational operators are as follows:

==, =, !=, <>, ~=. Valid values are "string", 'string', {GUID}, TRUE, FALSE, NULL.

Individual Boolean expressions can be joined with AND or OR. Expressions can be nested in parentheses to enforce a specific order of evaluation.

Following are some examples of valid query criteria:

"EventClassID == {F89859D1-6565-11D1-88C8-0080C7D771BF}"

"EventClassID == {F89859D1-6565-11D1-88C8-0080C7D771BF} AND MethodName = 'StockPriceChange'"

Requirements

Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header eventsys.h

See also

IMultiInterfaceEventControl