# Read and write data

Build the endpoints. Insert, query, and stream rows through the typed context sets with predicates instead of SQL.

With the context injected, the endpoints are a few lines each. Every set exposes typed reads and writes that take expression predicates, so the compiler checks your queries.

## Create a project

`InsertAsync` defaults `includeAutoFields` to `false`, so the `[Default]` columns (`Id`, `CreatedAt`) are left for the database to fill:

```csharp
app.MapPost("/projects", (Project project, ISocigyDatabaseFactory<IAppDb> db) =>
    db.ExecuteAsync(d => d.Projects.InsertAsync(project)));
```

## List a project's tasks

`ToListAsync` takes an optional predicate and materializes the rows inside the scope:

```csharp
app.MapGet("/projects/{id:guid}/tasks", (Guid id, ISocigyDatabaseFactory<IAppDb> db) =>
    db.ExecuteAsync(d => d.Tasks.ToListAsync(t => t.ProjectId == id)));
```

## Add a task

```csharp
app.MapPost("/projects/{id:guid}/tasks", (Guid id, TaskItem task, ISocigyDatabaseFactory<IAppDb> db) =>
{
    task.ProjectId = id;
    return db.ExecuteAsync(d => d.Tasks.InsertAsync(task));
});
```

## The set API

Each table set (`d.Projects`, `d.Tasks`) exposes:

| Method | Returns | Notes |
|--------|---------|-------|
| `ToListAsync(predicate?)` | `Task<List<T>>` | all rows, or those matching the predicate |
| `FirstOrDefaultAsync(predicate)` | `Task<T?>` | first match or `null` |
| `ExistsAsync(predicate)` | `Task<bool>` | existence check |
| `CountAsync(predicate?)` | `Task<long>` | `SELECT COUNT(*)` |
| `InsertAsync(entity, includeAutoFields = false)` | `Task<bool>` | one row |
| `InsertMultipleAsync(entities, ...)` | `Task<int>` | batched multi-row insert |
| `UpdateAsync(entity)` | `Task<int>` | update by primary key |
| `DeleteAsync(predicate)` | `Task<int>` | delete matching rows |
| `ForEachAsync(predicate, onRow)` | `Task` | stream rows without buffering |

To process many rows without loading them all into memory, stream with `ForEachAsync`:

```csharp
app.MapPost("/projects/{id:guid}/complete-all", (Guid id, ISocigyDatabaseFactory<IAppDb> db) =>
    db.ExecuteAsync(d => d.Tasks.ForEachAsync(t => t.ProjectId == id, async task =>
    {
        task.Done = true;
        await d.Tasks.UpdateAsync(task);
    })));
```

> **NOTE** The set methods (`d.Tasks.ToListAsync(...)`) are distinct from the static query builder (`TaskItem.Query(...)`). The builder is for standalone use with your own connection and is covered under [Querying](/database/0.3.2/querying/reading/select); the set methods run inside the context scope.

The last endpoint, creating a project and its tasks atomically, needs a transaction. Continue to [Transactions and tests](/database/0.3.2/tutorial/transactions-and-tests).