JackcessDotNet

Pure .NET 8 library for reading and writing Microsoft Access (.mdb / .accdb) files. No ODBC, no ACE drivers, no native dependencies — runs anywhere .NET 8 runs (Windows, Linux, macOS, containers).

This is a C# port of the spannm/jackcess Java project (a maintained fork of the original Jackcess by James Ahlborn). The upstream Java project remains the source of truth for the Jet file format; this port tracks its behaviour and reuses its test corpus for verification.

Install

dotnet add package JackcessDotNet

Quick start

using JackcessDotNet;

// Open an existing .mdb / .accdb (auto-detects version)
using var db = Database.Open("Northwind.mdb");

foreach (var name in db.ListTables())
    Console.WriteLine(name);

var customers = db.GetTable("Customers");
foreach (var row in customers.NewCursor())
    Console.WriteLine($"{row["CustomerID"]}  {row["CompanyName"]}");

// Create a new database, define a schema, insert rows
using var fresh = Database.Create("MyData.mdb", JetVersion.Jet4);
var people = fresh.CreateTable("People", new[]
{
    new ColumnBuilder("Id",   DataType.Long).Build(),
    new ColumnBuilder("Name", DataType.Text).MaxLength(50).Build(),
}, primaryKey: "Id");
people.Insert(new Row { ["Id"] = 1, ["Name"] = "Alice" });

Opening password-protected files

// Jet RC4 (.mdb, Access 97 / 2000–2003)
using var db = Database.Open("Confidential.mdb", "passw0rd");

// .accdb encryption — Agile (Office 2010+), ECMA Standard (Office 2007),
// RC4 CryptoAPI (Office 2002–2003), or Non-Standard AES — all auto-detected
// from the EncryptionInfo header.
using var db = Database.Open("Confidential.accdb", "passw0rd");

// Inspect which scheme the codec picked (useful when triaging an unfamiliar file).
byte[] page0 = File.ReadAllBytes("Confidential.accdb").Take(4096).ToArray();
var codec = OfficeCryptCodecHandler.FromDbHeader(page0, "passw0rd");
Console.WriteLine(codec?.Scheme);   // → "Agile Encryption (Office 2010+)"

Wrong passwords throw UnauthorizedAccessException before any data page is parsed — no cryptic "page X corrupt" errors.

Composite (multi-column) primary keys

db.CreateTable("Orders", new[]
{
    new ColumnBuilder("CustomerId", DataType.Long).Build(),
    new ColumnBuilder("OrderId",    DataType.Long).Build(),
    new ColumnBuilder("Total",      DataType.Money).Build(),
}, primaryKeyColumns: new[] { "CustomerId", "OrderId" });

Up to 10 columns per composite key (Jet's hard limit). The single-column primaryKey: overload still works for the common case.

Foreign-key enforcement on insert (opt-in)

using var db = Database.Open("Northwind.mdb");
db.EnforceForeignKeys = true;                  // default: false

// MSysRelationships drives validation. Any Insert whose FK column doesn't
// match an existing parent row throws InvalidOperationException.
orders.Insert(new Row { ["CustomerID"] = "INVALID", ... });
//                                                    ^ throws "Foreign-key violation in
//                                                              relationship 'CustomersOrders'..."

Null FK values are allowed (SQL semantics). Restrict-only — no cascade.

Importing from DataTable, DataSet, or IEnumerable<T>

Skip the schema boilerplate — the importer infers columns from the source type:

using var db = DatabaseImporter.CreateFromDataTable("out.mdb", myDataTable);

// or add into an existing database
db.ImportTable(otherDataTable, tableName: "Extra", primaryKey: "Id");
db.ImportTables(myDataSet);

db.ImportTable<Customer>(customers, primaryKey: "Id");

// Append rows into a pre-existing table (instead of failing):
db.ImportTable(moreRows, options: new ImportOptions { AppendIfExists = true });

POCO mapping respects [Key], [Column("X")], [MaxLength], [NotMapped], and [DatabaseGenerated(Identity)]. Long strings (>255 chars) auto-promote to Memo; large byte arrays (>255 bytes) to OLE. Unmappable types can fall back to Memo via ImportOptions.FallbackUnmappableToString = true.

Exporting back

DataTable          dt    = db.ExportToDataTable("Customers");
DataSet            ds    = db.ExportToDataSet();
IEnumerable<Customer> cs = db.ExportToCollection<Customer>("Customers");

The IEnumerable<T> path is lazy via yield, so Take(n) stops early without materialising the whole table.

Status

Feature	Status
Read Jet 3 (Access 97) / Jet 4 (Access 2000–2003)	✅
Read ACE 12 / 14 / 16 / 17 (.accdb)	✅
Create new .mdb files (Jet 4 / Jet 3)	✅
Row CRUD + B-tree indexes (single-column PK)	✅
Memo / OLE long values	✅
PropertyMap & MSysRelationships	✅
Password-protected .mdb (Jet RC4 codec)	✅
Password-protected .accdb (Agile Encryption, Office 2010+)	✅ Read + write¹
Password-protected .accdb (ECMA Standard Encryption, Office 2007)	✅ Read + write
Password-protected .accdb (RC4 CryptoAPI, Office 2002–2003)	✅ Read + write
Password-protected .accdb (Non-Standard AES, compat mode 0)	✅ Read + write
Password-protected .accdb (Extensible Encryption)	❌ External CSP — non-portable
Multi-column primary keys	✅
Foreign-key enforcement on insert (opt-in)	✅ Restrict-only
Queries (MSysQueries)	❌ Not yet

¹ Agile write doesn't recompute the DataIntegrity HMAC, so files modified through this library round-trip cleanly through Database.Open(path, password) but Office Access may flag a stale integrity hash. Matches the upstream jackcess-encrypt limitation.

Type round-trip cheat sheet

CLR type	Jet column	Notes
bool	Boolean
byte	Byte
short/ushort	Int (16-bit)	both come back as short
int/uint	Long (32-bit)	both come back as int
long/ulong	Long (32-bit)	truncated to 32 bits
float/double	Float/Double
decimal	Money	4-decimal precision; use Numeric for more
DateTime	ShortDateTime	Kind is dropped
DateTimeOffset	ShortDateTime	stored as UTC
Guid	Guid
string ≤255	Text
string >255	Memo	auto-promoted on MaxLength
byte[] ≤255	Binary
byte[] >255	Ole	auto-promoted on MaxLength
Nullable<T>	underlying T
enum	underlying type	round-trips back to the enum on read

Version history

See CHANGELOG.md — also shipped inside the .nupkg.

Credits

This project would not exist without the years of reverse-engineering work done by James Ahlborn (original Jackcess) and Markus Spann (maintained fork at spannm/jackcess). The Jet binary format is documented effectively only through their Java source.

License

Apache License 2.0 — same as the upstream Jackcess project.