Platform SDK: Transaction Server

ObjectContext Object

[This product will work only on Windows NT 4.0 versions and earlier. For Windows 2000 and later, see COM+ (Component Services).]

The ObjectContext object provides access to the current object's context.

Remarks

To use the ObjectContext object, you must set a reference to Microsoft Transaction Server Type Library (mtxas.dll).

You obtain a reference to the ObjectContext object by calling the GetObjectContext function. As with any COM object, you must release an ObjectContext object when you're finished using it, unless it's a local variable.

You can use an object's ObjectContext to:

Declare that the object's work is complete.
Prevent a transaction from being committed, either temporarily or permanently.
Instantiate other MTS objects and include their work within the scope of the current object's transaction.
Find out if a caller is in a particular role.
Find out if security is enabled.
Find out if the object is executing within a transaction.
Retrieve Microsoft Internet Information Server (IIS) built-in objects.

The ObjectContext object provides the following methods.

Method	Description
Count	Returns the number of context object properties.
CreateInstance	Instantiates another MTS object.
DisableCommit	Declares that the object hasn't finished its work and that its transactional updates are in an inconsistent state. The object retains its state across method calls, and any attempts to commit the transaction before the object calls EnableCommit or SetComplete will result in the transaction being aborted.
EnableCommit	Declares that the object's work isn't necessarily finished, but its transactional updates are in a consistent state. This method allows the transaction to be committed, but the object retains its state across method calls until it calls SetComplete or SetAbort, or until the transaction is completed.
IsCallerInRole	Indicates whether the object's direct caller is in a specified role (either directly or as part of a group).
IsInTransaction	Indicates whether the object is executing within a transaction.
IsSecurityEnabled	Indicates whether security is enabled. MTS security is enabled unless the object is running in the client's process.
Item	Returns a context object property.
Security	Returns a reference to an object's SecurityProperty object.
SetAbort	Declares that the object has completed its work and can be deactivated on returning from the currently executing method, but that its transactional updates are in an inconsistent state or that an unrecoverable error occurred. This means that the transaction in which the object was executing must be aborted. If any object executing within a transaction returns to its client after calling SetAbort, the entire transaction is doomed to abort.
SetComplete	Declares that the object has completed its work and can be deactivated on returning from the currently executing method. For objects that are executing within the scope of a transaction, it also indicates that the object's transactional updates can be committed. When an object that is the root of a transaction calls SetComplete, MTS attempts to commit the transaction on return from the current method.

Note When an object calls DisableCommit, EnableCommit, SetComplete, or SetAbort from within a method, two flags (Done and Consistent) are set in its ObjectContext. (See the following table for an explanation.) These flags aren't evaluated by the MTS run-time environment until the object's currently executing method returns to its caller. This means that an object can call these methods any number of times from within one of its own methods, but the last call before the object returns to its client is the one that will be in effect.

Method	Done	Consistent
SetAbort	TRUE	FALSE
SetComplete	TRUE	TRUE
DisableCommit	FALSE	FALSE
EnableCommit	FALSE	TRUE

The Done flag, which allows an object to be deactivated and its transaction to commit or abort, is only evaluated after the object returns from the call that first entered its context. For example, suppose client A calls into object B. Object B calls SetComplete and then calls into object C (passing it a safe reference for a callback). Object C calls back to object B, and then object B returns to client A. Object B won't be deactivated when it returns to object C; it will be deactivated when it returns to client A.