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Event sources in the .NET client

This page covers the .NET client’s API for event source definitions. The guides, the scenarios and the explanation of how they work are in Event sources and streams. This page lists the client types and where each is explained. An event source is optional: the existing append APIs remain valid and append events without a definition.

Types

Type	Purpose	Explained in
`IEventSource`	Marker interface. A class that implements it is a definition	Define an event source
`[EventSource]`	Names the definition and sets its description and default `Concurrency`	Define an event source
`[EventStream]`	Declares a stream, with its own description and `Concurrency`. Repeat it for each stream	Define an event source
`ConcurrencyDimensions`	Flags that choose which values take part in an append’s concurrency check	Concurrency
`Append<TSource>`, `AppendMany<TSource>`, `AppendPrepared<TSource>`	Extension methods on `IEventSequence`	Append through a definition
`EventForEventSourceId.EventSource` and `.EventStream`	Route one event of a multi-source batch through a definition	Append through a definition
`ConcurrencyScopeBuilder.ForEventSource<TSource>`	Builds an explicit scope from a definition’s names	Concurrency
`[FromEventSource<TSource>]`	Filters a reactor or reducer to one stream	Filter observers
`IEventStore.EventSources` and `IEventSources`	`All`, `GetFor(Type)` and `GetFor(string)` return the discovered `EventSourceDefinition` records	Define an event source
`IClientArtifactsProvider.EventSources`	The types the client treats as definitions	How it works

Exceptions

Exception	Thrown when
`DuplicateEventSourceName`	Two definitions share a name
`DuplicateEventStreamName`	A definition declares a stream twice
`UnknownEventSource`	A type or name is not a discovered definition
`EventStreamDoesNotBelongToEventSource`	A stream name is not declared by the definition
`EventRoutingContradictsEventSource`	An explicit event source type or stream type contradicts the definition
`IncompatibleConcurrencyScopesForEventSource`	A batch needs different guards for one event source id. See Concurrency
`EventSourcesNotSupported`	An `IEventStore` or `IEventSequence` implementation does not support event sources, such as a custom test double

Explicit registration

With explicit artifact registration you nominate the definitions in the composition root. A nominated event source keeps its declared streams and metadata, and an explicit name changes the registered identity only.

Dynamic Consistency Boundary in Chronicle: how definitions, decision reads and concurrency scopes relate to DCB.
Where the clients differ