1. Create the site
bash
dotnet new web -n Guestbook cd Guestbook dotnet add package NextGenSoftware.Holochain.HoloNET.API
2. Shared data: everyone sees it
Your own HoloNET API data is private to your agent. Shared data lives in a namespace that every agent in the app can read and write:
csharp
using NextGenSoftware.Holochain.HoloNET.API;
HoloNETAPI.UseConductor("ws://localhost:7777", logToConsole: false);
var app = WebApplication.Create(args);
app.MapPost("/api/guestbook", async (Entry e) =>
{
string key = DateTime.UtcNow.ToString("yyyyMMddHHmmssfff");
await HoloNETAPI.SaveSharedObjectAsync("guestbook", key, e); // stored on Holochain
return Results.Ok();
});
app.MapGet("/api/guestbook", async () =>
{
var keys = (await HoloNETAPI.ListSharedKeysAsync("guestbook", objects: true)).Result;
var entries = new List<Entry>();
foreach (var key in keys.OrderByDescending(k => k))
entries.Add((await HoloNETAPI.LoadSharedObjectAsync<Entry>("guestbook", key)).Result);
return entries;
});
app.Run();
public record Entry(string Name, string Message);
3. Live updates: hear when anyone changes it
Subscribe to the namespace. OnDataChanged fires whenever another agent changes it, whether that's another copy of your site or another app on Holochain. Push that to the browsers with Server-Sent Events:
csharp
await HoloNETAPI.SubscribeToChangesAsync("guestbook");
HoloNETAPI.OnDataChanged += (s, e) => NotifyBrowsers(e.Namespace); // e.Key, e.ByAgentPubKey, e.IsDeleted
The finished example has the whole Server-Sent Events endpoint and a page that re-loads the guestbook whenever it hears guestbook, so you can copy it from there.
4. Run it twice
Start it twice (on two ports, or on two machines in the same Holochain network) and open both pages. Sign the guestbook in one, and it appears in the other.
What just happened
- No database server. Each copy of the site runs its own Holochain agent, and they share the namespace through the hApp's DHT.
- Notifications travel directly from agent to agent as Holochain remote signals.
- Anyone can write to a namespace. If only some agents should be allowed to change something, add validation rules to your own hApp.
Next
- Real-time multiplayer with HyperNET, for traffic too fast for the DHT.
- The API guide covers shared objects, broadcasts and messages.