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Get started with the .NET client

Use the .NET client when you want direct typed access to Chronicle from a C# application. The smallest useful loop is:

  1. create a ChronicleClient
  2. open an event store
  3. append a fact to an event log
  4. let projections, reducers, and reactors observe that fact

Connect

Section titled “Connect”

For local development, start the Chronicle kernel and connect with the development connection string.

using Cratis.Chronicle;


using var client = new ChronicleClient(ChronicleConnectionString.Development);
var eventStore = await client.GetEventStore("Quickstart");

ChronicleConnectionString.Development points at the default local Chronicle kernel with development credentials. Use ChronicleConnectionString.Default or an explicit new ChronicleConnectionString("chronicle://...") when connecting to another environment.

Define an event

Section titled “Define an event”

Events are immutable facts. In .NET, mark event records with [EventType] so Chronicle can discover and register their schema.

using Cratis.Chronicle.Events;


[EventType]
public record BookAdded(string Title, string Isbn);

Append the event

Section titled “Append the event”

Append the event against the event source it belongs to. The event source id is not part of the event payload; Chronicle stores it in the event context.

var bookId = "book-123";


var result = await eventStore.EventLog.Append(
    bookId,
    new BookAdded("The Pragmatic Programmer", "978-0135957059"));


if (!result.IsSuccess)
{
    // Decide whether to retry or surface the append failure to the caller.
}

After the append succeeds, Chronicle persists the event and forwards it to the projections, reducers, reactors, and subscriptions that observe the event sequence.

Use a host integration

Section titled “Use a host integration”

For ASP.NET Core and Worker Service applications, prefer the host integration instead of creating the client manually:

builder.Services.AddCratisChronicle(options => options.EventStore = "Quickstart");

The host integration registers the event store, event log, read models, projections, reducers, reactors, constraints, and related services in dependency injection.

Next

Section titled “Next”