The PROPID_M_EXTENSION property is typically used by applications that need to specify or read non-MSMQ message properties when working with foreign queues.

The application is responsible to understand the content of this property.

To send extension information, specify PROPID_M_EXTENSION in the MQMSGPROPSstructure and call MQSendMessage.

To retrieve extension information, specify PROPID_M_EXTENSIONand PROPID_M_EXTENSION_LENin the MQMSGPROPSstructure. Then call MQReceiveMessageand examine the returned values.

Before using the returned value of PROPID_M_EXTENSION, inspect the returned value of PROPID_M_EXTENSION_LENto see if extension information was sent.

A returned value of 0 indicates that no information was sent by the sending application.

A nonzero returned value indicates the extension information was returned by PROPID_M_EXTENSION.

This property is not available when you use COM components.

The following examples show how PROPID_M_EXTENSION is specified in the MQMSGPROPSstructure for sending and retrieving extension information.

To send extension information

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aMsgPropId[i] = PROPID_M_EXTENSION; // Property ID aMsgPropVar[i].vt = VT_UI1 | VT_VECTOR; // Type indicator aMsgPropVar[i].caub.pElems = ExtensionInformation; aMsgPropVar[i].caub.cElems = sizeof(ExtensionInformation); i++;

To retrieve extension information

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aMsgPropId[i] = PROPID_M_EXTENSION_LEN; // Property ID aMsgPropVar[i].vt = VT_UI4; // Type indicator i++; aMsgPropId[i] = PROPID_M_EXTENSION; // Property ID aMsgPropVar[i].vt = VT_UI1 | VT_VECTOR; // Type indicator i++;

Note:
OS versions prior to 2.12 require the MSMQ add-on pack.