IEventControl::GetSubscriptions method (eventsys.h)

Article
10/13/2021

Retrieves the collection of subscriptions associated with an event method.

Syntax

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

Parameters

[in] methodName

The event method associated with the subscription collection.

[in] optionalCriteria

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

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

Return value

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

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

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