Plugin.Maui.LocalStore 1.0.1

Plugin.Maui.LocalStore

• NuGet: https://www.nuget.org/packages/Plugin.Maui.LocalStore
• GitHub: https://github.com/nuvyntralabs/Plugin.Maui.LocalStore
• Docs: https://nuvyntralabs.github.io/packages/plugin-maui-local-store/
• Catalog: MauiEssentials (Niladri Padhy / Nuvyntra Labs)

An abstract database layer for .NET MAUI on Android, iOS, Mac Catalyst, and Windows. The host picks an engine (StoreBackend). Application code always uses the same methods on ILocalStore / IStoreCollection<T>.

You do not change insert / find / replace / delete / select when you add or switch a backend. Each engine has its own file. Switching does not migrate data.

host always calls
  InsertAsync / InsertManyAsync / FindByIdAsync / ReplaceAsync / DeleteByIdAsync / FindAsync
                    ↓
              IStoreCollection<T>
     ┌────────────┼────────────┐
  SQLite      NuvexaDB     Realm / LiteDB / DuckDB
  SQLCipher   Firebird     LMDB / RocksDB / LevelDB

1.0 opens every engine in the table below. Host CRUD stays the same. See Platforms for which databases actually run on Android, iOS, Windows, and Mac Catalyst.

This is not JobQueue or RetryQueue (durable jobs). It is not OfflineSync (sync + conflicts). It is not androidx.room.

Package: https://www.nuget.org/packages/Plugin.Maui.LocalStore

Local / Embedded databases

Database	Type	Default path	MAUI	Offline	Relationships	Best for	Status
SQLite	Relational	app.db	⭐⭐⭐⭐⭐	✅	✅	General-purpose local DB	Shipped
NuvexaDB	Document NoSQL	app.nvx	⭐⭐⭐⭐⭐	✅	Limited	Embedded .nvx documents	Shipped
Realm	Object DB	app.realm	⭐⭐⭐⭐	✅	✅	Mobile / offline-first	Shipped
LiteDB	Document NoSQL	app.litedb	⭐⭐⭐⭐	✅	Limited	Embedded NoSQL	Shipped
DuckDB	Analytical SQL	app.duckdb	⭐⭐⭐	✅	✅	Analytics / OLAP	Shipped (JSON fallback on mobile)
SQLCipher	Encrypted SQLite	app.db	⭐⭐⭐⭐	✅	✅	Secure local DB	Shipped
Firebird Embedded	Relational	app.fdb	⭐⭐⭐	✅	✅	More advanced relational DB	Shipped (JSON fallback without fbembed)
LMDB	Key-value	app.lmdb/	⭐⭐⭐	✅	Limited	Very fast key-value storage	Shipped
RocksDB	Key-value	app.rocksdb/	⭐⭐⭐	✅	No	High-performance storage	Shipped (JSON fallback on mobile)
LevelDB	Key-value	app.leveldb/	⭐⭐⭐	✅	No	Simple KV storage	Shipped (JSON fallback when native is missing)

NuvexaDB is Nuventra.NuvexaDB (Nuvyntra Labs). Every row above is reached through the same IStoreCollection<T> methods.

Platforms

LocalStore targets Android, iOS, Windows, and Mac Catalyst. You still set StoreBackend the same way on every OS.

Yes = that database actually runs. JSON fallback = the NuGet has no native library for that OS, so LocalStore does not use the real engine.

Database	Android	iOS	Windows	Mac Catalyst
SQLite	Yes	Yes	Yes	Yes
SQLCipher	Yes	Yes	Yes	Yes
NuvexaDB	Yes	Yes	Yes	Yes
LiteDB	Yes	Yes	Yes	Yes
Realm	Yes	Yes	Yes	Yes
LMDB	Yes	Yes	Yes	JSON fallback
DuckDB	JSON fallback	JSON fallback	Yes (win-x64, win-arm64)	JSON fallback
Firebird	JSON fallback	JSON fallback	Yes (Embedded NuGet)	JSON fallback
RocksDB	JSON fallback	JSON fallback	Yes (win-x64 only)	JSON fallback
LevelDB	JSON fallback	JSON fallback	JSON fallback	JSON fallback

If you select a database on an unsupported platform

Selection does not change. Keep o.Backend = StoreBackend.DuckDb (or Firebird, RocksDB, LevelDB, or LMDB on Catalyst). LocalStore.Open / UseMauiLocalStore does not throw.

On that OS, LocalStore stores each row as a JSON file (app.duckdb.kv/, app.fdb.kv/, or files under app.lmdb/, app.rocksdb/, app.leveldb/). InsertAsync, FindByIdAsync, ReplaceAsync, DeleteByIdAsync, and FindAsync still work. Filters run in memory. EnsureIndexAsync does nothing.

This is not DuckDB / Firebird / RocksDB / LevelDB / LMDB. Switching later to a native file on a supported OS does not migrate those JSON rows. Use SQLite, SQLCipher, NuvexaDB, LiteDB, or Realm when you need the real engine on every MAUI platform.

Common methods

The host never writes SQL, NQL, or engine APIs on the shared path. Every backend must implement these operations:

Operation	Method
Create	InsertAsync / InsertManyAsync
Read	FindByIdAsync
Update	ReplaceAsync
Delete	DeleteByIdAsync
Select	FindAsync(StoreFilter, StoreQuery)
Index	EnsureIndexAsync
Close	DisposeAsync

ILocalStore store = LocalStore.Current;
var users = store.GetCollection<Person>("users");

POCOs need a public string Id (nullable is fine) and a public parameterless constructor. Filters use top-level property names (Age, City). Get-only or [JsonIgnore] members are not stored (the sample Person.Summary is ignored).

public sealed class Person
{
    public string? Id { get; set; }
    public string Name { get; set; } = "";
    public int Age { get; set; }
    public string Status { get; set; } = "active";
    public string? City { get; set; }
}

Scalar types: string, int, long, double, float, bool, DateTime.

dotnet add package Plugin.Maui.LocalStore

Host registration is UseMauiLocalStore. Non-MAUI hosts can call services.AddMauiLocalStore(...) or LocalStore.Open(...).

LocalStoreOptions.Backend defaults to StoreBackend.Nuvexa. Set it explicitly when you want SQLite or another engine. When Path is empty, the file is LocalApplicationData/Plugin.Maui.LocalStore/ plus the default path in the engine table above.

Option	Default	Used by
Backend	Nuvexa	All
Path	see ResolvePath	All (file or directory, per engine)
CreateIfMissing	true	All. false throws LocalStoreException if the file is missing
EncryptionKey	none	Nuvexa (required to open an encrypted .nvx), SQLCipher (required), LiteDB password, Realm, Firebird SYSDBA password. Ignored by SQLite, DuckDB, LMDB, RocksDB, LevelDB
CacheSizeMb	16	Nuvexa only

Library and sample share the OS TFMs: net10.0-android, net10.0-ios, net10.0-maccatalyst, plus net10.0-windows10.0.19041.0 when built on Windows. The library also packs net10.0 for tests and shared hosts.

The Create / Read / Update / Delete / Select samples in each engine section below are the same methods. Only StoreBackend and the file path change.

Engine NuGet references (library)

Backend	Package
SQLite	sqlite-net-base, SQLitePCLRaw.bundle_e_sqlite3
SQLCipher	same mapping + SQLitePCLRaw.bundle_e_sqlcipher (do not also reference sqlite-net-sqlcipher)
NuvexaDB	Nuventra.NuvexaDB 1.0.5
LiteDB	LiteDB
Realm	Realm
DuckDB	DuckDB.NET.Data.Full (desktop natives)
Firebird	FirebirdSql.Data.FirebirdClient, FirebirdDb.Embedded.V5.NativeAssets.Windows.All, FirebirdDb.Embedded.V5.NativeAssets.Linux.All
LMDB	LightningDB
RocksDB	RocksDB (desktop natives)
LevelDB	LevelDB.Standard with ExcludeAssets=native;build;buildTransitive (Android cannot load those native assets)

---

SQLite

Relational. File: app.db. One table per collection. EncryptionKey is ignored — use SQLCipher when you need an encrypted SQLite file.

Register

using Plugin.Maui.LocalStore;

builder
    .UseMauiApp<App>()
    .UseMauiLocalStore(o =>
    {
        o.Backend = StoreBackend.Sqlite;
        o.Path = Path.Combine(FileSystem.AppDataDirectory, "app.db");
        o.CreateIfMissing = true;
    });

var store = LocalStore.Current; // Backend == StoreBackend.Sqlite
var users = store.GetCollection<Person>("users");

Or without MAUI:

await using var store = LocalStore.Open(new LocalStoreOptions
{
    Backend = StoreBackend.Sqlite,
    Path = path
});

GetCollection creates the table on first write.

Create

var id = await users.InsertAsync(new Person
{
    Name = "Ada",
    Age = 36,
    Status = "active",
    City = "London"
});
// generated when Person.Id is null; written back onto the POCO

var ids = await users.InsertManyAsync(
[
    new Person { Name = "Grace", Age = 85, Status = "retired", City = "NewYork" },
    new Person { Name = "Cara", Age = 21, Status = "active", City = "Bengaluru" },
    new Person { Name = "Alan", Age = 42, Status = "active", City = "London" }
]);

Read

var ada = await users.FindByIdAsync(id);
if (ada is null)
{
    return;
}

Update

ReplaceAsync requires a non-empty Id. It updates the row; it does not insert. Missing id throws LocalStoreException.

ada.Name = "Ada Lovelace";
await users.ReplaceAsync(ada);

Delete

var removed = await users.DeleteByIdAsync(id);
// false when the id is not present

Select

FindAsync with no filter returns every row. StoreQuery.Limit of 0 means no limit. SQLite runs this as SQL on the table columns.

var all = await users.FindAsync();

var adults = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Limit = 20 });

var page2 = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Skip = 20, Limit = 20 });

var londonActive = await users.FindAsync(
    StoreFilter.And(
        StoreFilter.Eq("City", "London"),
        StoreFilter.Eq("Status", "active")),
    new StoreQuery { SortBy = "Age", SortDescending = true });

var youngOrNy = await users.FindAsync(
    StoreFilter.Or(
        StoreFilter.Lt("Age", 30),
        StoreFilter.Eq("City", "NewYork")));

var notRetired = await users.FindAsync(StoreFilter.Ne("Status", "retired"));

Filter	Meaning
StoreFilter.Eq("City", "London")	equal
StoreFilter.Ne("Status", "retired")	not equal
StoreFilter.Gte("Age", 21)	greater than or equal
StoreFilter.Lt("Age", 30)	less than
StoreFilter.And(...)	all children
StoreFilter.Or(...)	any child

await users.EnsureIndexAsync("Age");
await users.EnsureIndexAsync("City", "Status");

Close and delete the file

await store.DisposeAsync();
File.Delete(path);

---

NuvexaDB

Document NoSQL. File: app.nvx. One collection per name. Set EncryptionKey for AES-256-GCM. Opening an encrypted file without the key throws NuvexaEncryptionException (fail-closed). Store the key in SecureStorage — not in source.

Engine: Nuventra.NuvexaDB — GitHub.

Register

using Plugin.Maui.LocalStore;

builder
    .UseMauiApp<App>()
    .UseMauiLocalStore(o =>
    {
        o.Backend = StoreBackend.Nuvexa;
        o.Path = Path.Combine(FileSystem.AppDataDirectory, "app.nvx");
        o.EncryptionKey = key;
        o.CreateIfMissing = true;
        o.CacheSizeMb = 16;
    });

var store = LocalStore.Current; // Backend == StoreBackend.Nuvexa
var users = store.GetCollection<Person>("users");

Or without MAUI:

await using var store = LocalStore.Open(new LocalStoreOptions
{
    Backend = StoreBackend.Nuvexa,
    Path = path,
    EncryptionKey = key
});

GetCollection creates the collection on first write. Same Person type and same method names as every other engine.

Create

var id = await users.InsertAsync(new Person
{
    Name = "Ada",
    Age = 36,
    Status = "active",
    City = "London"
});

var ids = await users.InsertManyAsync(
[
    new Person { Name = "Grace", Age = 85, Status = "retired", City = "NewYork" },
    new Person { Name = "Cara", Age = 21, Status = "active", City = "Bengaluru" },
    new Person { Name = "Alan", Age = 42, Status = "active", City = "London" }
]);

Read

var ada = await users.FindByIdAsync(id);
if (ada is null)
{
    return;
}

Update

ada.Name = "Ada Lovelace";
await users.ReplaceAsync(ada);

Delete

var removed = await users.DeleteByIdAsync(id);

Select

Same StoreFilter / StoreQuery as SQLite. Nuvexa maps POCO names to NQL paths (Age → age, Id → _id).

var all = await users.FindAsync();

var adults = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Limit = 20 });

var page2 = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Skip = 20, Limit = 20 });

var londonActive = await users.FindAsync(
    StoreFilter.And(
        StoreFilter.Eq("City", "London"),
        StoreFilter.Eq("Status", "active")),
    new StoreQuery { SortBy = "Age", SortDescending = true });

var youngOrNy = await users.FindAsync(
    StoreFilter.Or(
        StoreFilter.Lt("Age", 30),
        StoreFilter.Eq("City", "NewYork")));

var notRetired = await users.FindAsync(StoreFilter.Ne("Status", "retired"));

await users.EnsureIndexAsync("Age");
await users.EnsureIndexAsync("City", "Status");

Close and delete the file

await store.DisposeAsync();
File.Delete(path);
var wal = path + "-wal";
if (File.Exists(wal))
{
    File.Delete(wal);
}

Engine-only: NQL

Optional. Not part of the common layer. Other engines have no NQL.

if (store is INuvexaLocalStore nuvexa)
{
    var rows = await nuvexa.ExecuteNqlAsync(
        """db.users.find({ age: { $gte: 21 } }).sort({ name: 1 }).limit(20)""");
}

NQL update / delete needs NuvexaDB 1.0.2+.

---

Realm

Object database. File: app.realm. Host POCOs stay plain classes. Rows are stored as JSON on a Realm object. Live Realm thread confinement is handled inside the adapter. Optional EncryptionKey encrypts the Realm file.

Register

builder.UseMauiLocalStore(o =>
{
    o.Backend = StoreBackend.Realm;
    o.Path = Path.Combine(FileSystem.AppDataDirectory, "app.realm");
    o.CreateIfMissing = true;
});

var users = LocalStore.Current.GetCollection<Person>("users");

Create

var id = await users.InsertAsync(new Person
{
    Name = "Ada", Age = 36, Status = "active", City = "London"
});

var ids = await users.InsertManyAsync(
[
    new Person { Name = "Grace", Age = 85, Status = "retired", City = "NewYork" },
    new Person { Name = "Cara", Age = 21, Status = "active", City = "Bengaluru" },
    new Person { Name = "Alan", Age = 42, Status = "active", City = "London" }
]);

Read

var ada = await users.FindByIdAsync(id);

Update

ada!.Name = "Ada Lovelace";
await users.ReplaceAsync(ada);

Delete

var removed = await users.DeleteByIdAsync(id);

Select

var all = await users.FindAsync();

var adults = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Limit = 20 });

var page2 = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Skip = 20, Limit = 20 });

var londonActive = await users.FindAsync(
    StoreFilter.And(
        StoreFilter.Eq("City", "London"),
        StoreFilter.Eq("Status", "active")),
    new StoreQuery { SortBy = "Age", SortDescending = true });

var youngOrNy = await users.FindAsync(
    StoreFilter.Or(
        StoreFilter.Lt("Age", 30),
        StoreFilter.Eq("City", "NewYork")));

var notRetired = await users.FindAsync(StoreFilter.Ne("Status", "retired"));

await users.EnsureIndexAsync("Age");
await users.EnsureIndexAsync("City", "Status");

---

LiteDB

Embedded document NoSQL. File: app.litedb. Closest peer to Nuvexa on the common API: named collections, BSON-style documents, limited relationships. Optional EncryptionKey becomes the LiteDB password.

Register

builder.UseMauiLocalStore(o =>
{
    o.Backend = StoreBackend.LiteDb;
    o.Path = Path.Combine(FileSystem.AppDataDirectory, "app.litedb");
    o.CreateIfMissing = true;
});

var users = LocalStore.Current.GetCollection<Person>("users");

Create

var id = await users.InsertAsync(new Person
{
    Name = "Ada", Age = 36, Status = "active", City = "London"
});

var ids = await users.InsertManyAsync(
[
    new Person { Name = "Grace", Age = 85, Status = "retired", City = "NewYork" },
    new Person { Name = "Cara", Age = 21, Status = "active", City = "Bengaluru" },
    new Person { Name = "Alan", Age = 42, Status = "active", City = "London" }
]);

Read

var ada = await users.FindByIdAsync(id);

Update

ada!.Name = "Ada Lovelace";
await users.ReplaceAsync(ada);

Delete

var removed = await users.DeleteByIdAsync(id);

Select

var all = await users.FindAsync();

var adults = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Limit = 20 });

var page2 = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Skip = 20, Limit = 20 });

var londonActive = await users.FindAsync(
    StoreFilter.And(
        StoreFilter.Eq("City", "London"),
        StoreFilter.Eq("Status", "active")),
    new StoreQuery { SortBy = "Age", SortDescending = true });

var youngOrNy = await users.FindAsync(
    StoreFilter.Or(
        StoreFilter.Lt("Age", 30),
        StoreFilter.Eq("City", "NewYork")));

var notRetired = await users.FindAsync(StoreFilter.Ne("Status", "retired"));

await users.EnsureIndexAsync("Age");
await users.EnsureIndexAsync("City", "Status");

---

DuckDB

Analytical SQL (OLAP). File: app.duckdb. Same CRUD; FindAsync maps to SQL. DuckDB.NET.Data.Full ships desktop natives only. On Android / iOS, LocalStore keeps the same IStoreCollection<T> API on a managed JSON folder (app.duckdb.kv).

Register

builder.UseMauiLocalStore(o =>
{
    o.Backend = StoreBackend.DuckDb;
    o.Path = Path.Combine(FileSystem.AppDataDirectory, "app.duckdb");
    o.CreateIfMissing = true;
});

var users = LocalStore.Current.GetCollection<Person>("users");

Create

var id = await users.InsertAsync(new Person
{
    Name = "Ada", Age = 36, Status = "active", City = "London"
});

var ids = await users.InsertManyAsync(
[
    new Person { Name = "Grace", Age = 85, Status = "retired", City = "NewYork" },
    new Person { Name = "Cara", Age = 21, Status = "active", City = "Bengaluru" },
    new Person { Name = "Alan", Age = 42, Status = "active", City = "London" }
]);

Read

var ada = await users.FindByIdAsync(id);

Update

ada!.Name = "Ada Lovelace";
await users.ReplaceAsync(ada);

Delete

var removed = await users.DeleteByIdAsync(id);

Select

var all = await users.FindAsync();

var adults = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Limit = 20 });

var page2 = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Skip = 20, Limit = 20 });

var londonActive = await users.FindAsync(
    StoreFilter.And(
        StoreFilter.Eq("City", "London"),
        StoreFilter.Eq("Status", "active")),
    new StoreQuery { SortBy = "Age", SortDescending = true });

var youngOrNy = await users.FindAsync(
    StoreFilter.Or(
        StoreFilter.Lt("Age", 30),
        StoreFilter.Eq("City", "NewYork")));

var notRetired = await users.FindAsync(StoreFilter.Ne("Status", "retired"));

await users.EnsureIndexAsync("Age");
await users.EnsureIndexAsync("City", "Status");

---

SQLCipher

Encrypted SQLite. File: app.db. Same relational mapping as SQLite. EncryptionKey is required. Do not reuse an unencrypted SQLite file as a SQLCipher path.

Register

builder.UseMauiLocalStore(o =>
{
    o.Backend = StoreBackend.SqlCipher;
    o.Path = Path.Combine(FileSystem.AppDataDirectory, "app-cipher.db");
    o.EncryptionKey = key;
    o.CreateIfMissing = true;
});

var users = LocalStore.Current.GetCollection<Person>("users");

Create

var id = await users.InsertAsync(new Person
{
    Name = "Ada", Age = 36, Status = "active", City = "London"
});

var ids = await users.InsertManyAsync(
[
    new Person { Name = "Grace", Age = 85, Status = "retired", City = "NewYork" },
    new Person { Name = "Cara", Age = 21, Status = "active", City = "Bengaluru" },
    new Person { Name = "Alan", Age = 42, Status = "active", City = "London" }
]);

Read

var ada = await users.FindByIdAsync(id);

Update

ada!.Name = "Ada Lovelace";
await users.ReplaceAsync(ada);

Delete

var removed = await users.DeleteByIdAsync(id);

Select

var all = await users.FindAsync();

var adults = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Limit = 20 });

var page2 = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Skip = 20, Limit = 20 });

var londonActive = await users.FindAsync(
    StoreFilter.And(
        StoreFilter.Eq("City", "London"),
        StoreFilter.Eq("Status", "active")),
    new StoreQuery { SortBy = "Age", SortDescending = true });

var youngOrNy = await users.FindAsync(
    StoreFilter.Or(
        StoreFilter.Lt("Age", 30),
        StoreFilter.Eq("City", "NewYork")));

var notRetired = await users.FindAsync(StoreFilter.Ne("Status", "retired"));

await users.EnsureIndexAsync("Age");
await users.EnsureIndexAsync("City", "Status");

Do not reuse an unencrypted SQLite app.db as a SQLCipher path. Dispose, then open a different file.

---

Firebird Embedded

Advanced relational. File: app.fdb. Same table-per-collection mapping as SQLite. The host still calls IStoreCollection<T>. Desktop opening needs a Firebird 5 embedded tree (FIREBIRD pointing at the folder that contains lib/, plugins/, and bin/isql). Windows and Linux can use the FirebirdDb.Embedded.V5.NativeAssets.* packages. macOS has no NuGet native assets — use the official Firebird 5 package and set FIREBIRD / FIREBIRD_CLIENT. Android / iOS / Mac Catalyst have no fbembed package; LocalStore uses the managed JSON folder (app.fdb.kv) so CRUD still works. Optional EncryptionKey is the SYSDBA password on a real Firebird file (masterkey when omitted). Switching backends does not migrate data.

Register

builder.UseMauiLocalStore(o =>
{
    o.Backend = StoreBackend.Firebird;
    o.Path = Path.Combine(FileSystem.AppDataDirectory, "app.fdb");
    o.CreateIfMissing = true;
});

var users = LocalStore.Current.GetCollection<Person>("users");

Create

var id = await users.InsertAsync(new Person
{
    Name = "Ada", Age = 36, Status = "active", City = "London"
});

var ids = await users.InsertManyAsync(
[
    new Person { Name = "Grace", Age = 85, Status = "retired", City = "NewYork" },
    new Person { Name = "Cara", Age = 21, Status = "active", City = "Bengaluru" },
    new Person { Name = "Alan", Age = 42, Status = "active", City = "London" }
]);

Read

var ada = await users.FindByIdAsync(id);

Update

ada!.Name = "Ada Lovelace";
await users.ReplaceAsync(ada);

Delete

var removed = await users.DeleteByIdAsync(id);

Select

var all = await users.FindAsync();

var adults = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Limit = 20 });

var page2 = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Skip = 20, Limit = 20 });

var londonActive = await users.FindAsync(
    StoreFilter.And(
        StoreFilter.Eq("City", "London"),
        StoreFilter.Eq("Status", "active")),
    new StoreQuery { SortBy = "Age", SortDescending = true });

var youngOrNy = await users.FindAsync(
    StoreFilter.Or(
        StoreFilter.Lt("Age", 30),
        StoreFilter.Eq("City", "NewYork")));

var notRetired = await users.FindAsync(StoreFilter.Ne("Status", "retired"));

await users.EnsureIndexAsync("Age");
await users.EnsureIndexAsync("City", "Status");

---

LMDB

Key-value. Path: app.lmdb (directory). Each collection is a key prefix. The POCO is stored as JSON keyed by Id. FindAsync filters in memory. EnsureIndexAsync is a no-op. Relationships are limited.

Register

builder.UseMauiLocalStore(o =>
{
    o.Backend = StoreBackend.Lmdb;
    o.Path = Path.Combine(FileSystem.AppDataDirectory, "app.lmdb");
    o.CreateIfMissing = true;
});

var users = LocalStore.Current.GetCollection<Person>("users");

Create

var id = await users.InsertAsync(new Person
{
    Name = "Ada", Age = 36, Status = "active", City = "London"
});

var ids = await users.InsertManyAsync(
[
    new Person { Name = "Grace", Age = 85, Status = "retired", City = "NewYork" },
    new Person { Name = "Cara", Age = 21, Status = "active", City = "Bengaluru" },
    new Person { Name = "Alan", Age = 42, Status = "active", City = "London" }
]);

Read

var ada = await users.FindByIdAsync(id);

Update

ada!.Name = "Ada Lovelace";
await users.ReplaceAsync(ada);

Delete

var removed = await users.DeleteByIdAsync(id);

Select

var all = await users.FindAsync();

var adults = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Limit = 20 });

var page2 = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Skip = 20, Limit = 20 });

var londonActive = await users.FindAsync(
    StoreFilter.And(
        StoreFilter.Eq("City", "London"),
        StoreFilter.Eq("Status", "active")),
    new StoreQuery { SortBy = "Age", SortDescending = true });

var youngOrNy = await users.FindAsync(
    StoreFilter.Or(
        StoreFilter.Lt("Age", 30),
        StoreFilter.Eq("City", "NewYork")));

var notRetired = await users.FindAsync(StoreFilter.Ne("Status", "retired"));

await users.EnsureIndexAsync("Age");
await users.EnsureIndexAsync("City", "Status");

---

RocksDB

Key-value. Path: app.rocksdb (directory). High-write LSM storage. Same Id → JSON mapping as LMDB. FindAsync scans the prefix and filters in memory. EnsureIndexAsync is a no-op. The RocksDB NuGet ships desktop natives only. On Android / iOS, LocalStore uses the same managed per-key JSON files as LevelDB.

Register

builder.UseMauiLocalStore(o =>
{
    o.Backend = StoreBackend.RocksDb;
    o.Path = Path.Combine(FileSystem.AppDataDirectory, "app.rocksdb");
    o.CreateIfMissing = true;
});

var users = LocalStore.Current.GetCollection<Person>("users");

Create

var id = await users.InsertAsync(new Person
{
    Name = "Ada", Age = 36, Status = "active", City = "London"
});

var ids = await users.InsertManyAsync(
[
    new Person { Name = "Grace", Age = 85, Status = "retired", City = "NewYork" },
    new Person { Name = "Cara", Age = 21, Status = "active", City = "Bengaluru" },
    new Person { Name = "Alan", Age = 42, Status = "active", City = "London" }
]);

Read

var ada = await users.FindByIdAsync(id);

Update

ada!.Name = "Ada Lovelace";
await users.ReplaceAsync(ada);

Delete

var removed = await users.DeleteByIdAsync(id);

Select

var all = await users.FindAsync();

var adults = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Limit = 20 });

var page2 = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Skip = 20, Limit = 20 });

var londonActive = await users.FindAsync(
    StoreFilter.And(
        StoreFilter.Eq("City", "London"),
        StoreFilter.Eq("Status", "active")),
    new StoreQuery { SortBy = "Age", SortDescending = true });

var youngOrNy = await users.FindAsync(
    StoreFilter.Or(
        StoreFilter.Lt("Age", 30),
        StoreFilter.Eq("City", "NewYork")));

var notRetired = await users.FindAsync(StoreFilter.Ne("Status", "retired"));

await users.EnsureIndexAsync("Age");
await users.EnsureIndexAsync("City", "Status");

---

LevelDB

Key-value. Path: app.leveldb (directory). Same collection + Id contract as RocksDB. FindAsync filters in memory. EnsureIndexAsync is a no-op. If the native LevelDB library is missing for the RID (osx-arm64 is not in LevelDB.Standard; Android native assets are excluded because they are not PE), LocalStore uses a managed per-key JSON file store so the same API still works.

Register

builder.UseMauiLocalStore(o =>
{
    o.Backend = StoreBackend.LevelDb;
    o.Path = Path.Combine(FileSystem.AppDataDirectory, "app.leveldb");
    o.CreateIfMissing = true;
});

var users = LocalStore.Current.GetCollection<Person>("users");

Create

var id = await users.InsertAsync(new Person
{
    Name = "Ada", Age = 36, Status = "active", City = "London"
});

var ids = await users.InsertManyAsync(
[
    new Person { Name = "Grace", Age = 85, Status = "retired", City = "NewYork" },
    new Person { Name = "Cara", Age = 21, Status = "active", City = "Bengaluru" },
    new Person { Name = "Alan", Age = 42, Status = "active", City = "London" }
]);

Read

var ada = await users.FindByIdAsync(id);

Update

ada!.Name = "Ada Lovelace";
await users.ReplaceAsync(ada);

Delete

var removed = await users.DeleteByIdAsync(id);

Select

var all = await users.FindAsync();

var adults = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Limit = 20 });

var page2 = await users.FindAsync(
    StoreFilter.Gte("Age", 21),
    new StoreQuery { SortBy = "Name", Skip = 20, Limit = 20 });

var londonActive = await users.FindAsync(
    StoreFilter.And(
        StoreFilter.Eq("City", "London"),
        StoreFilter.Eq("Status", "active")),
    new StoreQuery { SortBy = "Age", SortDescending = true });

var youngOrNy = await users.FindAsync(
    StoreFilter.Or(
        StoreFilter.Lt("Age", 30),
        StoreFilter.Eq("City", "NewYork")));

var notRetired = await users.FindAsync(StoreFilter.Ne("Status", "retired"));

await users.EnsureIndexAsync("Age");
await users.EnsureIndexAsync("City", "Status");

---

Add another database later

A new engine implements ILocalStore / IStoreCollection<T> and a StoreBackend value. Host code stays on the common methods. Dispose, then Open with the new backend and a different path — data does not copy.

await LocalStore.Current.DisposeAsync();
LocalStore.Open(new LocalStoreOptions
{
    Backend = StoreBackend.Sqlite, // or Nuvexa, Realm, LiteDb, DuckDb, SqlCipher, Firebird, Lmdb, RocksDb, LevelDb
    Path = Path.Combine(FileSystem.AppDataDirectory, "app.db")
});

CreateIfMissing = false throws LocalStoreException when the file is missing.

What 1.0 does not do

• Automatic migration between engines
• Source-generated DAOs or raw SQL / NQL on the shared interface
• Automatic promotion from the JSON fallback to a later native DuckDB / Firebird / RocksDB / LevelDB file
• Sibling PackageReference to OfflineSync, JobQueue, or FileVault

Sample

samples/Plugin.Maui.LocalStore.Sample uses the same OS TFMs as the library: net10.0-android, net10.0-ios, net10.0-maccatalyst, and net10.0-windows10.0.19041.0 when the sample is built on Windows. MauiProgram does not call UseMauiLocalStore — the Backend picker calls LocalStore.Open so you can walk every engine. A host app that uses one engine should register it with UseMauiLocalStore.

Use insert / update / delete / find by Id, FindAsync presets (all, Age ≥ 21, London AND active, Age < 30 OR NewYork, custom), Seed, Reset file, Contract tour, and Test all engines. DuckDB, Firebird, and RocksDB pass on device via the JSON fallback (they are not silent skips). SQLCipher uses app-cipher.db so it does not share the SQLite app.db.

License

MIT