csharp-server

# SpacetimeDB C# SDK Reference ## Module Structure Reducers are static methods in a `static partial class`; tables are `public partial struct`s. This reference keeps everything in one `public static partial class Module`, which needs only `using SpacetimeDB;`: Methods exported through SpacetimeDB attributes, including reducers, procedures, views, HTTP handlers, and routers, must be `public static`; generated bindings invoke them from another class. ```csharp using SpacetimeDB; public static partial class Module { [SpacetimeDB.Table(Accessor = "ScoreRecord", Public = true)] public partial struct ScoreRecord { [PrimaryKey] [AutoInc] public ulong Id; public Identity Owner; public uint Value; } [SpacetimeDB.Reducer] public static void AddRecord(ReducerContext ctx, uint value) { ctx.Db.ScoreRecord.Insert(new ScoreRecord { Id = 0, Owner = ctx.Sender, Value = value }); } } ``` ## Tables `[SpacetimeDB.Table(...)]` on a `public partial struct`. `Accessor` should be PascalCase: ```csharp [SpacetimeDB.Table(Accessor = "Entity", Public = true)] public partial struct Entity { [PrimaryKey] [AutoInc] public ulong Id; [SpacetimeDB.Index.BTree] public Identity Owner; public string Name; [SpacetimeDB.Index.BTree] public bool Active; } ``` Options: `Accessor = "PascalCase"` (recommended), `Public = true`, `Scheduled = nameof(ReducerFn)`, `ScheduledAt = nameof(field)`, `Event = true` `ctx.Db` accessors use the `Accessor` name: `ctx.Db.Entity`, `ctx.Db.ScoreRecord`. ## Column Types | C# type | Notes | |---------|-------| | `byte` / `ushort` / `uint` / `ulong` | unsigned integers | | `U128` / `U256` | large unsigned integers (SpacetimeDB types) | | `sbyte` / `short` / `int` / `long` | signed integers | | `I128` / `I256` | large signed integers (SpacetimeDB types) | | `float` / `double` | floats | | `bool` | boolean | | `string` | text | | `List<T>` | list/array | | `Identity` | user identity | | `ConnectionId` | connection handle | | `Timestamp` | server timestamp (microseconds since epoch) | | `TimeDuration` | duration in microseconds | | `Uuid` | UUID | Optional columns: nullable types (`string? Nickname`, `uint? HighScore`) ## Column Attributes The complete set of column attributes: ```csharp [PrimaryKey] // primary key [AutoInc] // auto-increment (use 0 as placeholder on insert) [Unique] // unique constraint; indexes the column, enables .Find() [SpacetimeDB.Index.BTree] // btree index (enables .Filter() on this column) [Default(true)] // migration-safe default for a newly appended field ``` Defaults support compatible addition of a newly appended field. Do not apply `[Default(...)]` to primary-key, unique, or auto-increment fields. ## Indexes Write the index attribute fully qualified: `[SpacetimeDB.Index.BTree]`. Prefer inline for single-column; multi-column uses struct-level: ```csharp // Inline (preferred for single-column): [SpacetimeDB.Index.BTree] public ulong AuthorId; // Access: ctx.Db.Post.AuthorId.Filter(authorId) // Multi-column (struct-level): [SpacetimeDB.Table(Accessor = "Membership")] [SpacetimeDB.Index.BTree(Accessor = "ByGroupUser", Columns = new[] { nameof(GroupId), nameof(UserId) })] public partial struct Membership { public ulong GroupId; public Identity UserId; ... } ``` Prefer a multi-column index over filtering by one column and looping. ## Reducers ```csharp [SpacetimeDB.Reducer] public static void CreateEntity(ReducerContext ctx, string name, int age) { ctx.Db.Entity.Insert(new Entity { Owner = ctx.Sender, Name = name, Age = age, Active = true }); } // No arguments: [SpacetimeDB.Reducer] public static void DoReset(ReducerContext ctx) { ... } ``` ## DB Operations ```csharp var row = ctx.Db.Entity.Insert(new Entity { Name = "Sample" }); // Insert; returns the row with AutoInc fields assigned ctx.Db.Entity.Id.Find(entityId); // Find by PK → Entity? (nullable) ctx.Db.Entity.Identity.Find(ctx.Sender); // Find by unique column → Entity? if (ctx.Db.Entity.Id.Find(entityId) is { } entity) { ... } // unwrap Entity? before member access ctx.Db.Item.AuthorId.Filter(authorId); // Filter by index → IEnumerable<Item> ctx.Db.Entity.Iter(); // All rows → IEnumerable<Entity> ctx.Db.Entity.Count; // Count rows ctx.Db.Entity.Id.Update(existing with { Name = newName }); // Update by PK ctx.Db.Entity.Id.Delete(entityId); // Delete by PK ``` Note: Filter/Iter return enumerables. Use `.ToList()` if you need to sort or mutate. The pattern is `ctx.Db.{Accessor}.{ColumnName}.{Method}(value)` for all indexed column operations. ## Lifecycle Hooks ```csharp [SpacetimeDB.Reducer(ReducerKind.Init)] public static void OnInit(ReducerContext ctx) { ... } [SpacetimeDB.Reducer(ReducerKind.ClientConnected)] public static void OnConnect(ReducerContext ctx) { ... } [SpacetimeDB.Reducer(ReducerKind.ClientDisconnected)] public static void OnDisconnect(ReducerContext ctx) { ... } ``` `ctx.ConnectionId` is `ConnectionId?`, including in connection lifecycle reducers. Check or unwrap it before storing it in a non-nullable column or passing it to an index accessor. ## Views ```csharp // Anonymous view (same result for all clients): [SpacetimeDB.View(Accessor = "ActiveUsers", Public = true)] public static List<Entity> ActiveUsers(AnonymousViewContext ctx) { return ctx.Db.Entity.Active.Filter(true).ToList(); } // Per-user view: [SpacetimeDB.View(Accessor = "MyEntities", Public = true)] public static List<Entity> MyEntities(ViewContext ctx) { return ctx.Db.Entity.Owner.Filter(ctx.Sender).ToList(); } ``` View contexts expose read-only table handles. These support `Count` plus `Find`/`Filter` on declared indexes, but not full-table `Iter()`. Start procedural view traversal from an indexed lookup or filter. Query-builder views use `ViewContext`, `ctx.From`, and return `IQuery<T>` directly. Use `Where` for predicates and `RightSemijoin` when the result should contain right-side rows that have a matching left-side row: ```csharp ctx.From.Article().Where(article => article.Published.Eq(true)); ctx.From.Subscription().RightSemijoin( ctx.From.Account(), (subscription, account) => subscription.AccountId.Eq(account.Id) ); ``` Declare a procedural view primary key in its attribute: `[SpacetimeDB.View(Accessor = "CatalogEntry", Public = true, PrimaryKey = nameof(CatalogRow.Sku))]`. Procedural-view primary keys are explicit schema metadata. Add one only when the view itself is required to expose a primary key; a source table's primary key is not inherited by the view. Inclusive btree ranges use tuples, for example `ctx.Db.Shipment.DeliverBy.Filter((new Timestamp(1_000), new Timestamp(2_000)))`. ## Client Visibility Filters ```csharp [ClientVisibilityFilter] public static readonly Filter PrivateNoteFilter = new Filter.Sql( "SELECT * FROM OwnedRow WHERE Owner = :sender" ); ``` ## Reducer Context API `ReducerContext` (`ctx`) is the only source of sender identity, time, and randomness; stdlib clocks and RNG are unavailable in modules. ```csharp // Auth: ctx.Sender is the caller's Identity if (row.Owner != ctx.Sender) throw new Exception("unauthorized"); // Server timestamp (deterministic per reducer call) ctx.Db.Item.Insert(new Item { CreatedAt = ctx.Timestamp, .. }); // Timestamp arithmetic var expiry = ctx.Timestamp + new TimeDuration(delayMicros); // Deterministic RNG int roll = ctx.Rng.Next(1, 7); // [1, 7): inclusive 1, exclusive 7 double f = ctx.Rng.NextDouble(); // [0.0, 1.0) // Timestamp → milliseconds since epoch timestamp.MicrosecondsSinceUnixEpoch / 1000 ``` ## Scheduled Tables Declare the scheduled table and its reducer in the same `Module` class so `nameof(...)` resolves: ```csharp [SpacetimeDB.Table( Accessor = "TickTimer", Scheduled = nameof(Tick), ScheduledAt = nameof(ScheduledAt), Public = true )] public partial struct TickTimer { [PrimaryKey] [AutoInc] public ulong ScheduledId; public ScheduleAt ScheduledAt; } [SpacetimeDB.Reducer] public static void Tick(ReducerContext ctx, TickTimer timer) { // timer row is auto-deleted after this reducer runs } // One-time: fires once at a specific time var at = new ScheduleAt.Time(ctx.Timestamp + new TimeDuration(10_000_000)); // Repeating: fires on an interval var at = new ScheduleAt.Interval(TimeSpan.FromSeconds(5)); ctx.Db.TickTimer.Insert(new TickTimer { ScheduledId = 0, ScheduledAt = at }); ``` Scheduled reducer callbacks use the ordinary `[SpacetimeDB.Reducer]` attribute. There is no `ReducerKind.Scheduled`; the table's `Scheduled` option associates the callback. To construct a `ConnectionId` from a 128-bit numeric representation, encode it as exactly 16 little-endian bytes and call `ConnectionId.From(bytes)`. The result is nullable and must be checked before use. ## Procedures and HTTP Procedures are unstable APIs, so modules using them should include `#pragma warning disable STDB_UNSTABLE`. They receive `ProcedureContext` and may return `[SpacetimeDB.Type]` values: ```csharp [SpacetimeDB.Type] public partial struct ResultValue { public string Value; } [SpacetimeDB.Procedure] public static ResultValue Inspect(ProcedureContext ctx, string input) => new() { Value = input }; ``` Outbound HTTP is available through `ctx.Http`; handle its success/error result before using the response. Open short database transactions with `ctx.WithTx`. Perform network I/O before opening the transaction, and keep only database work inside its callback. ```csharp var result = ctx.Http.Get(uri); var text = result.Match( response => response.Body.ToStringUtf8Lossy(), error => throw new Exception(error.Message) ); ctx.WithTx(tx => { tx.Db.ScoreRecord.Insert(new ScoreRecord { Id = 0, Owner = ctx.Sender, Value = 1 }); return 0; }); ``` `WithTx` is generic: its callback must return a value (use `return 0;` when no result is needed). The callback's generated `tx.Db` exposes module table accessors; `ProcedureContext` and `HandlerContext` do not expose tables directly. For non-GET requests, construct and send an `HttpRequest` directly: ```csharp var result = ctx.Http.Send(new HttpRequest { Uri = uri, Method = SpacetimeDB.HttpMethod.Post, Headers = new() { new HttpHeader("content-type", "text/plain") }, Body = HttpBody.FromString(payload), }); ``` `HttpResponse.StatusCode` is `ushort`. HTTP headers are `HttpHeader` values, not tuples, and each header's `Value` is `byte[]`; decode text values with `System.Text.Encoding.UTF8.GetString(header.Value)`. Treat bodies as bytes: use `HttpBody.FromString(...)` to create text, `new HttpBody(bytes)` to supply raw bytes, `ToBytes()` to read raw bytes, and `ToStringUtf8Lossy()` to read text. There is no `HttpBody.FromBytes`, and `ToString()` does not return body contents. Qualify `SpacetimeDB.HttpMethod` when .NET's implicit `System.Net.Http` imports could make the name ambiguous. Scheduled procedures use the ordinary scheduled-table shape. Its `Scheduled` name refers to a `[SpacetimeDB.Procedure]` method taking `ProcedureContext` plus the scheduled row, and database access inside that procedure goes through `ctx.WithTx`. Inbound HTTP uses handler attributes and one router. Handler database access also goes through `ctx.WithTx`: ```csharp [SpacetimeDB.HttpHandler] public static HttpResponse Health(HandlerContext ctx, HttpRequest request) => new( 200, HttpVersion.Http11, new(), HttpBody.FromString("ok") ); [SpacetimeDB.HttpRouter] public static Router Routes() => SpacetimeDB.Router.New().Get("/health", Handlers.Health); ``` `Handlers` is generated from methods marked `[SpacetimeDB.HttpHandler]`; do not declare it yourself. Reference an attributed method in a router as `Handlers.MethodName`. ## Custom Types ```csharp [SpacetimeDB.Type] public enum Status { Online, Away, Offline } [SpacetimeDB.Type] public partial struct Point { public float X; public float Y; } ``` Tagged enums (discriminated unions): a `partial record` with empty body and no constructor parameters. Payloads are `[Type] partial struct`s: ```csharp [SpacetimeDB.Type] public partial struct Circle { public int Radius; } [SpacetimeDB.Type] public partial struct Rectangle { public int Width; public int Height; } [SpacetimeDB.Type] public partial record Shape : SpacetimeDB.TaggedEnum<(Circle Circle, Rectangle Rectangle)> { } // Construct variants via the generated nested constructors: var a = new Shape.Circle(new Circle { Radius = 10 }); var b = new Shape.Rectangle(new Rectangle { Width = 4, Height = 6 }); ```