csharp-client

# SpacetimeDB C# Client Install: `dotnet add package SpacetimeDB.ClientSDK` Generated bindings convert snake_case names to PascalCase, including row fields: a server column `trip_id` is `TripId` on client rows. ## Connection ```csharp using SpacetimeDB; using SpacetimeDB.Types; var conn = DbConnection.Builder() .WithUri("http://localhost:3000") .WithDatabaseName("my-database") .WithToken(savedToken) .WithCompression(Compression.Brotli) // optional; this is the default .OnConnect((conn, identity, token) => { Console.WriteLine($"Connected as: {identity}"); // Save token for reconnection File.WriteAllText("auth_token.txt", token); conn.SubscriptionBuilder() .OnApplied(OnSubscriptionApplied) .SubscribeToAllTables(); }) .OnConnectError(err => Console.Error.WriteLine($"Connection failed: {err}")) .OnDisconnect((conn, err) => { if (err != null) Console.Error.WriteLine($"Disconnected: {err}"); }) .Build(); ``` Compression options are `Compression.Brotli`, `Compression.Gzip`, and `Compression.None`. The SDK uses Brotli when `WithCompression` is omitted. ## Automatic Reconnect and Token Refresh Automatic reconnect is opt-in: add `.WithAutomaticReconnect()` to the builder. Initial connection failures do not retry. After an established connection is lost, the SDK retries with exponential backoff and jitter from `MinDelay` (default 1 s) up to `MaxDelay` (default 30 s); tune them with `.WithAutomaticReconnect(new AutomaticReconnectOptions { MinDelay = ..., MaxDelay = ... })`. Values below the 500 ms and 1 s floors are raised with a warning, so that retrying clients cannot overwhelm the database. `Disconnect()` permanently stops recovery. Keep calling `FrameTick()` while `IsActive` is false. `IsReconnecting` is true while recovering before the next handshake. Use `.OnDisconnect((conn, error, next) => ...)` and `.OnConnectError((error, next) => ...)` to inspect `NextReconnect?`: a non-null value provides `Attempt` and `Delay`; null means no retry is scheduled. Existing callback overloads still work. `OnConnect` runs on every successful reconnect, so create the subscription in the example above only on the first connection, or move it after `Build()`. Register row callbacks once as well. The same connection, identity, table handles, and subscriptions survive; each attempt gets a fresh `ConnectionId`. Cached rows stay readable but stale during outages. The SDK replays subscriptions in one batch and emits only net row changes. Subscription `OnApplied` runs again after replay; use it to mark data ready, not for repeated one-time setup. For expiring credentials, combine `.WithToken(initialToken)` with `.WithTokenProvider(() => RefreshTokenAsync())`, where your provider returns `Task<string>` for the same identity. The provider is not called for the initial connection. Before retries, it is called when remaining validity is at most 30 seconds or 5% of the token lifetime, whichever is greater, when expiry cannot be read, or after a reused token is rejected. Provider failures retry; rejection of a freshly provided token is terminal. No periodic refresh runs while connected. Disconnecting ignores a pending provider result but does not cancel the provider's own work. Calls made while disconnected fail immediately. Pending reducer calls receive `Status.UnknownResult`; pending procedures and one-off queries fail with `UnknownResultException`. These calls may already have executed and are never replayed. Regenerate bindings so unhandled unknown reducer outcomes reach `OnUnhandledReducerError`. ## Event Loop (Critical) **`FrameTick()` must be called in your main loop.** The SDK queues all network messages and only processes them when you call `FrameTick()`. Without it, no callbacks fire. ```csharp while (running) { conn.FrameTick(); // Your application logic... Thread.Sleep(16); // ~60fps } ``` **Thread safety**: `FrameTick()` processes messages on the calling thread. Do NOT call it from a background thread. Do NOT access `conn.Db` from background threads. ## Subscriptions ```csharp // Subscribe to all tables conn.SubscriptionBuilder() .OnApplied(ctx => Console.WriteLine("Subscription ready")) .SubscribeToAllTables(); // Subscribe with typed query builder (recommended) conn.SubscriptionBuilder() .OnApplied(OnSubscriptionApplied) .AddQuery(q => q.From.Player().Where(p => p.Level.Gte(5u))) .AddQuery(q => q.From.GameState()) .Subscribe(); // Or with raw SQL strings conn.SubscriptionBuilder() .OnApplied(OnSubscriptionApplied) .Subscribe(new[] { "SELECT * FROM player WHERE level >= 5", "SELECT * FROM game_state" }); ``` ## Row Callbacks ```csharp conn.Db.Player.OnInsert += (EventContext ctx, Player player) => { Console.WriteLine($"Player joined: {player.Name}"); }; conn.Db.Player.OnDelete += (EventContext ctx, Player player) => { Console.WriteLine($"Player left: {player.Name}"); }; conn.Db.Player.OnUpdate += (EventContext ctx, Player oldPlayer, Player newPlayer) => { Console.WriteLine($"Player updated: {newPlayer.Name}"); }; ``` ## Reading the Client Cache ```csharp // Find by primary key if (conn.Db.Player.Id.Find(playerId) is Player player) { Console.WriteLine($"Player: {player.Name}"); } // Find by unique column var me = conn.Db.Player.Identity.Find(myIdentity); // Filter by indexed column foreach (var p in conn.Db.Player.Level.Filter(5)) { Console.WriteLine($"Level 5: {p.Name}"); } // Iterate all rows foreach (var p in conn.Db.Player.Iter()) { Console.WriteLine(p.Name); } // Count int total = conn.Db.Player.Count; ``` ## Calling Reducers ```csharp conn.Reducers.CreatePlayer("Alice"); conn.Reducers.MovePlayer(10.0f, 20.0f); conn.Reducers.SendMessage("Hello!"); ``` Reducer calls return `void`; observe failures via the reducer callbacks below (`Status.Failed`). ## Reducer Callbacks ```csharp conn.Reducers.OnSendMessage += (ReducerEventContext ctx, string text) => { if (ctx.Event.Status is Status.Committed) Console.WriteLine($"Message sent: {text}"); else if (ctx.Event.Status is Status.Failed(var reason)) Console.Error.WriteLine($"Send failed: {reason}"); else if (ctx.Event.Status is Status.UnknownResult) Console.Error.WriteLine("Connection lost before the result arrived; the message may have been sent."); }; ``` ## Identity ```csharp // Identities from OnConnect callback Identity myIdentity; // Compare identities if (player.Owner == myIdentity) { /* it's me */ } // Display Console.WriteLine($"Identity: {identity}"); ```