Conventions

Conventions

A convention is a way of defining what a certain type is instead of using an interface or an attribute. Using conventions along with avoiding references to NServiceBus assemblies is referred to as unobtrusive mode. This is ideal for use in cross-platform environments.

Currently conventions exist to identify:

Messages can be defined in a Portable Class Library (PCL) and shared across multiple platforms even if the platform does not use NServiceBus for message processing.

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var conventions = endpointConfiguration.Conventions();
conventions.DefiningCommandsAs(type => type.Namespace == "MyNamespace.Messages.Commands");
conventions.DefiningEventsAs(type => type.Namespace == "MyNamespace.Messages.Events");
conventions.DefiningMessagesAs(type => type.Namespace == "MyNamespace.Messages");
conventions.DefiningDataBusPropertiesAs(property => property.Name.EndsWith("DataBus"));
conventions.DefiningExpressMessagesAs(type => type.Name.EndsWith("Express"));
conventions.DefiningTimeToBeReceivedAs(type => type.Name.EndsWith("Expires") ? TimeSpan.FromSeconds(30) : TimeSpan.MaxValue);

Note that in .NET, the namespace is optional and hence can be null. If any conventions do partial string checks, for example using EndsWith or StartsWith, then a null check should be used. So include .Namespace != null at the start of the convention. Otherwise a null reference exception will occur during the type scanning.

Using both default and custom conventions

Defining conventions will replace any of the existing conventions. If both default and custom conventions are needed it is required to embed the NServiceBus marker interfaces/types into the new custom conventions.

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var conventions = endpointConfiguration.Conventions();
conventions.DefiningCommandsAs(type =>
    type.Namespace == "MyNamespace.Messages.Commands"
    || typeof(ICommand).IsAssignableFrom(type)
);
conventions.DefiningEventsAs(type =>
    type.Namespace == "MyNamespace.Messages.Events"
    || typeof(IEvent).IsAssignableFrom(type)
);
conventions.DefiningMessagesAs(type =>
    type.Namespace == "MyNamespace.Messages"
    || typeof(IMessage).IsAssignableFrom(type)
);
conventions.DefiningDataBusPropertiesAs(property =>
    property.Name.EndsWith("DataBus")
    || typeof(IDataBusProperty).IsAssignableFrom(property.PropertyType) && typeof(IDataBusProperty) != property.PropertyType
);
conventions.DefiningExpressMessagesAs(type =>
    type.Name.EndsWith("Express")
    || type.GetCustomAttribute<ExpressAttribute>(true) != null
);
conventions.DefiningTimeToBeReceivedAs(type =>
    type.Name.EndsWith("Expires")
        ? TimeSpan.FromSeconds(30)
        : type.GetCustomAttribute<TimeToBeReceivedAttribute>(false)?.TimeToBeReceived ?? TimeSpan.MaxValue
);

Attributes

If attributes are preferred over marker interfaces then this can be achieved via NServiceBus.AttributeConventions, a community package that allows using attributes instead of interfaces.

Using both default and custom conventions

Attributes

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