Versioning

In this sample there are two message projects: V1.Messages and V2.Messages:

namespace V1.Messages
{
    public interface ISomethingHappened :
        IEvent
    {
        int SomeData { get; set; }
    }
}

The Version 2 message schema inherits from the version 1 schema as shown below, adding another property on top of the properties in the version 1 schema.

namespace V2.Messages
{
    public interface ISomethingHappened :
        V1.Messages.ISomethingHappened
    {
        string MoreInfo { get; set; }
    }
}

There are two subscribers as before, but now one subscriber is subscribed to the version 1 message schema, V1Subscriber; and the other subscriber is subscribed to the Version 2 message schema, V2Subscriber.

<UnicastBusConfig>
  <MessageEndpointMappings>
    <add Assembly="V1.Messages"
         Endpoint="Samples.Versioning.V2Publisher"/>
  </MessageEndpointMappings>
</UnicastBusConfig>

While V2Subscriber has this in its UnicastBusConfig:

<UnicastBusConfig>
  <MessageEndpointMappings>
    <add Assembly="V2.Messages"
         Endpoint="Samples.Versioning.V2Publisher"/>
  </MessageEndpointMappings>
</UnicastBusConfig>

The only difference is that each subscriber maps the version of the schema on which it is dependent.

Look at V2Publisher, which is very similar to the publisher from the PubSub sample. The only thing that V2Publisher is doing is publishing a message from the Version 2 schema. However, the sample is run, V1Subscriber receives these messages as well:

Publisher output

Press 'Enter' to publish a message, Ctrl + C to exit.
Published event.

V1Subscriber output

Press any key to stop program
Something happened with some data 1 and no more info

V2Subscriber output

Press any key to stop program
Something happened with some data 1 and more information It's a secret.