DKNet

Capture a save-time snapshot for hooks

Part of DKNet.EfCore.Extensions. Keep the entries and their pre-save states available after EF Core has changed tracking state.

Use the console-project setup in the Quick Start, then replace Program.cs with this example.

using Microsoft.EntityFrameworkCore;
using DKNet.EfCore.Extensions.Snapshots;

using var connection = new Microsoft.Data.Sqlite.SqliteConnection("Data Source=:memory:");
connection.Open();
var o = new DbContextOptionsBuilder<DemoDb>();
o.UseSqlite(connection);
await using var db = new DemoDb(o.Options);
db.Add(new Item { Name = "Coffee" });
using var snapshot = new SnapshotContext(db);
snapshot.Initialize();
Console.WriteLine(snapshot.Entities.Single().OriginalState); // Added

public sealed class DemoDb(DbContextOptions<DemoDb> options) : DbContext(options)
{
    public DbSet<Item> Items => Set<Item>();
}
public sealed class Item
{
    public int Id { get; set; }
    public string Name { get; set; } = "";
}

SnapshotEntityEntry retains the live Entry and Entity references plus the copied OriginalState. Disposal clears the captured list and leaves the DbContext and its tracker settings untouched.

🧱 Where it fits

Hooks creates one SnapshotContext per save. EventHook, EfCoreAuditHook and DataOwnerHook inspect its entries through their hook callbacks; they do not each build a separate capture.

⚠️ Gotchas & limits

• Read Entities only after Initialize; otherwise it throws InvalidOperationException. Access after disposal throws ObjectDisposedException.
• Initialize appends to the list. Use a fresh snapshot per save rather than calling Initialize repeatedly.
• This is not a deep copy of property values. Live entity and entry values may change after capture; capture values separately if needed.
• Entities added later are absent. The Hooks pipeline captures once before hooks and shares that snapshot with the after phase.

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