Your first zome call

1. Start a conductor

Holochain apps run on a conductor, the Holochain runtime on your machine. The examples folder has a script that starts a throwaway one, using the binaries bundled with HoloNET:

examples/start-conductor.sh            # or, in PowerShell:  .\examples\start-conductor.ps1

Leave it running. Its admin interface is on ws://localhost:7777, HoloNET's default.

2. Create the project

dotnet new console -n MyFirstHapp
cd MyFirstHapp
dotnet add package NextGenSoftware.Holochain.HoloNET.Client

You'll also need a .happ file: the OASIS hApp works well. It's oasis.happ in the HoloNET API package, or in HoloNET-API/NextGenSoftware.Holochain.HoloNET.API/ in the repo. Copy it next to your project.

3. Connect, and install the hApp in one call

using NextGenSoftware.Holochain.HoloNET.Client;

var admin = new HoloNETClientAdmin(new HoloNETDNA
{
    HolochainConductorAdminURI = "ws://localhost:7777",
    AutoStartHolochainConductor = false,      // we started it ourselves
    AutoShutdownHolochainConductor = false
});
await admin.ConnectAsync();

var app = await admin.InstallEnableSignAttachAndConnectToHappAsync("my-first-app", "oasis.happ", "oasis");
if (!app.IsAppConnected) throw new Exception(app.Message);
var client = app.HoloNETClientAppAgent;
Console.WriteLine("My agent: " + app.AgentPubKey);

That one call does everything Holochain 0.7 needs: 1. Generates an agent key. 2. Installs the hApp. 3. Enables it. 4. Sets up signing and a capability grant. 5. Attaches an app interface and issues an authentication token. 6. Connects an app client.

4. Write an entry, and read it back

var created = await client.CallZomeFunctionAsync("oasis", "create_entry_avatar", new Dictionary<string, object>
{
    ["id"] = Guid.NewGuid().ToString(), ["username"] = "ada", ["email"] = "ada@example.com"
});
string actionHash = created.Records[0].ActionHash;

var read = await client.CallZomeFunctionAsync("oasis", "get_entry_avatar", client.ConvertHoloHashToBytes(actionHash));
Console.WriteLine("Read back: " + read.Records[0].EntryKeyValuePairs["username"]);

• The parameters. The dictionary's keys must match the fields of the Rust struct in the zome.
• The hash. An entry is identified by its ActionHash. You use it to read, update and delete it.
• Errors. Zome errors don't throw. Check created.IsError and created.Message.

5. Run it

dotnet run

What just happened

• No server. Your app talked to your own conductor.
• Where the data lives. The avatar entry went onto your agent's source chain (its own signed history), and was published to the hApp's DHT, which every agent in the app shares.
• Signed calls. HoloNET signed every zome call with your agent's key.

Next

• Save data in one line with HoloNET API, without zome calls at all.
• The Client guide covers signals, the admin API, clone cells and more.