The message that the server should publish in the event of an ungraceful disconnection.
This property may be set before calling Connect to specify to the server a message that should be published on WillTopic if the connection is closed ungracefully. Since it is sent to the server when Connect is called, this property's value cannot be changed when already connected.
Refer to WillTopic for more information about MQTT Will functionality.
This property is not available at design time.