File Cannot Open

Fix Access Workgroup Information File Errors in C# Application

Muhammad Talha Sep 28, 2026 869 views

Question details

The user needs to resolve an OLE DB connection error in a C# application indicating that an Access workgroup information file is missing or opened exclusively.

How to Fix Access Workgroup Information File Errors in a C# Application

Product: Microsoft Access / C#
Device & OS: not provided
Scenario: Connecting to a password-protected or secured Access database from a C# application using an OLE DB connection string.
Observed behavior: The C# application throws an exception stating the workgroup information file is missing or opened exclusively by another user when attempting to connect to the database.

Before you start

Ensure no other users, background processes, or open instances of Microsoft Access are locking the database or MDW file in exclusive mode before testing your C# connection string.

Solution 1Recommended

Update Connection String for Password-Protected Database

Use this solution if your database is encrypted with a password but does not use an MDW file for user-level security.

Many connection errors occur when developers mistakenly include workgroup parameters for a database that only requires a standard password. Adjusting the connection string to match the encryption type is the most direct fix.

Verify encryption method

Determine if the Access database is simply password-protected rather than secured with user-level security (MDW). Open Microsoft Access, click 'File', then 'Info' to check the encryption status.

Modify the connection string

In your C# code or App.config file, remove any 'SystemDB' parameters from your OLE DB connection string, as they are not needed for basic password encryption.

Add the database password

Append 'Jet OLEDB:Database Password=YourPassword;' to your connection string. For example: 'Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\path\database.accdb;Jet OLEDB:Database Password=MySecret;'.

Update Connection String for Password-Protected Database

Connection Provider: Make sure you are using 'Microsoft.ACE.OLEDB.12.0' (or later) for newer .accdb files, whereas 'Microsoft.Jet.OLEDB.4.0' is generally used for older .mdb files.

Solution 2

Configure the MDW File Path in Connection String

Apply this method if your Access database relies on user-level security via an MDW workgroup information file.

Solution 3

Resolve Exclusive Lock Issues

Use this fix if the connection string is correct but the application still reports the file is opened exclusively by another user.

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Frequently Asked Questions

What is an MDW file in Microsoft Access?

An MDW file is a Workgroup Information File used by older versions of Microsoft Access to store user-level security data, including user accounts, passwords, and granular permissions for database objects.

Why do I get an 'opened exclusively by another user' error?

This error occurs when a user, an application, or a lingering background process has opened the database or the MDW file in exclusive mode. This prevents any other external C# application from establishing an OLE DB connection.

How do I connect to an Access database without an MDW file?

If the database only uses standard password encryption without user-level security, omit the SystemDB parameter entirely. Simply include the 'Jet OLEDB:Database Password=[your_password]' parameter in your C# connection string.

Document & File Issues