---

The idea

A timeline accepts short entries. Every entry becomes an immutable TimelineEntryRecorded event in Chronicle, and the API can read the complete history for one timeline.

flowchart LR
    client[HTTP client] --> api[ASP.NET Core API]
    api --> timeline[Timeline]
    timeline -->|append| log[Chronicle event log]
    log -->|history| timeline

There is no projection, database abstraction, frontend, or messaging layer in the way. This sample is about the event log itself.

Run it

You need the .NET 10 SDK, Docker, and curl.

Start Chronicle:

docker run --rm --name chronicle-backend-sample \
  -p 35000:35000 \
  -p 8080:8080 \
  cratis/chronicle:latest-development

Start the API from the repository root:

dotnet run --project Chronicle/Backend/Backend.csproj --urls http://localhost:5095

The sample uses the ChronicleBackend event store and Chronicle's default namespace.

Record something that happened

TIMELINE_ID=7d9d3f76-0c2d-4a93-a67b-d8f8fb2bc941

curl --request POST \
  --header 'Content-Type: application/json' \
  --data '{"text":"Chronicle keeps the facts."}' \
  "http://localhost:5095/api/timelines/${TIMELINE_ID}/entries"

The API responds with 201 Created and Chronicle's sequence number for the appended event.

Read the history

curl "http://localhost:5095/api/timelines/${TIMELINE_ID}/history"

You will get the entries recorded for that timeline in event-log order. Open Chronicle Workbench at http://localhost:8080 and select ChronicleBackend to inspect the same history visually.

Code tour

File	What it shows
Program.cs	The complete Chronicle and ASP.NET Core setup
TimelineId.cs	A strongly typed EventSourceId<Guid> identity
TimelineEntryText.cs	A ConceptAs<string> domain value instead of a raw string
TimelineEntryRecorded.cs	A small, past-tense event built from that domain value
Timeline.cs	Append and history operations against IEventLog
TimelineEndpoints.cs	Two focused HTTP endpoints

The host setup is intentionally short:

var builder = WebApplication.CreateBuilder(args)
    .AddCratisChronicle(options => options.EventStore = "ChronicleBackend");

var app = builder.Build();
app.UseCratisChronicle();

Build and test

dotnet build Chronicle/Backend/Backend.csproj
dotnet test Chronicle/Backend/Backend.Specs/Backend.Specs.csproj

The small specification project checks the append and history behavior without requiring a running Chronicle container.

Make it yours

• Add a second kind of timeline event.
• Return different history shapes for different questions.
• Move on to the Processing sample when you want projections, reducers, and reactions.