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CONNECT Attributes Sample: Demonstrates Implementation and Use of Connection Points

The CONNECT attributes sample illustrates the implementation and use of connection points (the IConnectionPointContainer and IConnectionPoint interfaces) in a multithreaded environment.

The sample demonstrates several commonly used IDL, COM, and compiler attributes, including support_errorinfo, event_source, and event_receiver.

Security noteSecurity Note:

This sample code is provided to illustrate a concept and should not be used in applications or Web sites, as it may not illustrate the safest coding practices. Microsoft assumes no liability for incidental or consequential damages should the sample code be used for purposes other than as intended.

To get samples and instructions for installing them:

  • On the Visual Studio Help menu, click Samples.

    For more information, see Visual Studio Samples.

  • The most recent version and complete list of samples is available online from the Visual Studio 2008 Samples page.

  • You can also locate samples on your computer's hard disk. By default, samples and a Readme file are copied into a folder under \Program Files\Visual Studio 9.0\Samples\. For Express editions of Visual Studio, all samples are located online.

To build and run this sample

  1. Open the solution file connect.sln.

  2. From the Build menu, click Build Solution.

  3. Select which client you want to run, Drive or MDrive, and make it the startup project (right-click the project folder and click Set as StartUp Project). More information about the clients can be found in the How the Sample Works section.

  4. On the Debug menu, click Start Without Debugging.

The server is implemented in Connect.dll. This DLL allows the creation of a CoRandom COM object, implemented by the CRandom C++ class. The COM object supports IRandom (a dual interface) and IConnectionPointContainer, and it accepts connections for the IRandomEvent interface.

The IRandom interface supports the following methods:

  • Start — starts a thread inside the object

  • Stop — stops a thread inside the object

  • StopAll — stops all of the running threads

When running, the secondary threads inside the object keep firing events through the connection point.

Two clients are provided: Drive and MDrive. They can be found in the Drive and MDrive subdirectories.

  • Drive.exe is a simple console application that provides a single object implementing the IRandomEvent interface. It creates a CoRandom object, calls Advise and Unadvise on the connection point, and makes the CoRandom object fire events into the drive's object.

  • Mdrive.exe is an MFC dialog-based application, able to create multiple advise sinks and control the number of threads the server creates. When you run Mdrive.exe, click the Start button at least once, then click the Advise button several times. Each click of the Advise button adds a connection point, which makes the display wider. If you do not click the Advise button, you will not see any activity in the display.

This sample uses the following attributes:

  • Connect   coclass, default, dll, dual, event_source, helpstring, id, in, module, name, object, out, pointer_default, progid, support_error_info, uuid, vi_progid

  • Connect/drive   event_receiver, module

This sample uses the following keywords:

AfxGetApp; AfxMessageBox; AtlAdvise; ATLASSERT; AtlUnadvise; BEGIN_COM_MAP; BEGIN_CONNECTION_POINT_MAP; BEGIN_MESSAGE_MAP; BEGIN_OBJECT_MAP; CComCoClass; CComModule::GetClassObject; CComModule::GetLockCount; CComModule::Init; CComModule::RegisterServer; CComModule::Term; CComModule::UnregisterServer; CComObject::CreateInstance; CComObjectRoot; CDialog::OnCancel; CDialog::OnOK; CloseHandle; CoCreateInstance; COleTemplateServer::RegisterAll; COM_INTERFACE_ENTRY; COM_INTERFACE_ENTRY_IMPL; COM_INTERFACE_ENTRY2; CONNECTION_POINT_ENTRY; CoUninitialize; CreateEvent; CreateThread; DECLARE_REGISTRY_RESOURCEID; DisableThreadLibraryCalls; DoModal; DrawIcon; END_COM_MAP; END_CONNECTION_POINT_MAP; END_MESSAGE_MAP; END_OBJECT_MAP; GdiFlush; GetClientRect; GetDlgItem; GetTickCount; GetUnknown; IConnectionPointContainerImpl; IConnectionPointImpl; IDispatchImpl; ISupportErrorInfo; LoadIcon; Lock; memset; OBJECT_ENTRY; ON_COMMAND; puts; ReleaseDC; SendMessage; SetEvent; SetIcon; SetPixel; Sleep; Unadvise; Unlock; WaitForSingleObject

NoteNote:

Some of the samples, such as this one, have not been modified to reflect the changes in the Visual C++ wizards, libraries, and compiler, but still demonstrate how to complete your desired task.

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