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This property of the MSMQMessageobject, introduced in MSMQ 2.0, specifies additional application-defined information that is associated with the message.

This property is used by connector applications.


Variant (array of bytes)

Run time:






Message ( MSMQMessage) object that represents the message.

Property Values

Application-defined information.


The MSMQMessage.Extensionproperty is used by connector applications to process non-Message Queuing message properties when translating between Message Queuing messages and foreign messages.

It is the responsibility of the sending application, connector application, and the receiving application to understand the content of this property.

Visual Basic arrays

When dimensioning arrays for extension data, always set the lower boundary of the array to 0.

When filling in the extension data, Message Queuing sets the lower boundary of the returned byte-array to 0 regardless of what boundary was set by the application.

The following Microsoft Visual Basic® call always returns 0.

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Equivalent Function property

When using functions, the extension property of the message can be set and retrieved using the PROPID_M_EXTENSION property.


Header mqoai.h
Library mqoa.lib
Windows Embedded CE Windows CE .NET 4.0 and later
Windows Mobile Windows Mobile Version 5.0 and later