An Azure relational database service.
It's hard to know without the exact error you're getting, but Managed Identity Auth (MSI) is only available with Microsoft.Data.SqlClient 2.1.0 or newer. If you're using a user-assigned managed identity, you'll need to specify either the client id (v3+) or object id (v2.1), like so: // With Microsoft.Data.SqlClient v3.0+ string ConnectionString1 = @"Server=demo.database.windows.net; Authentication=Active Directory Managed Identity; Encrypt=True; User Id=ClientIdOfManagedIdentity; Database=testdb";