The AccessDataSource.DataFile property is a virtual, absolute, or UNC directory path to the Access .mdb file that the System.Web.UI.WebControls.AccessDataSource control represents. If only the name of the file is entered, this indicates that the .mdb file is found in the same directory as the currently executing Web Forms page or code. Relative paths with both forward and backward slashes are supported. For example, "./test/test/Northwind.mdb" maps to the same path as ".\test\test\Northwind.mdb" and "test/test/Northwind.mdb". UNC paths, such as "\\mymachine\somedatadirectory\Northwind.mdb", are also supported. Although absolute physical paths are supported, you should avoid using them because they can complicate deployment.

Configuring Permissions for an Access Database

An important aspect of working with an Access .mdb file is to configure permissions properly. When a Web application uses an Access database, the application must have Read permission to the .mdb file so that it can access the data. In addition, the application must have Write permission to the folder containing the .mdb file. Write permission is required because Access creates an additional file with the extension .ldb in which it maintains information about database locks for concurrent users. The .ldb file is created at run time.

By default, ASP.NET Web applications run in the context of a local machine account called ASPNET (for Microsoft Windows 2000 and Microsoft Windows XP), or in the context of the NETWORK SERVICE account (for Microsoft Windows Server 2003). For example, for Windows 2000 or Windows XP, if the Web server is named MyServer, ASP.NET applications on the MyServer computer run in the context of the local account MyServer\ASPNET.

Therefore, to use an Access database in an ASP.NET Web application, you must configure the folder containing the Access database to have both Read and Write permissions.

When you create a Web site in the Microsoft Visual Web Developer Web development tool, Visual Web Developer creates a folder named App_Data below the current root folder. The folder is designed to be a store for application data, including Access databases. The App_Data folder is also used by ASP.NET to store databases that the system maintains, such as the database for membership and roles. When Visual Web Developer creates the App_Data folder, it grants Read and Write permissions for the folder to the ASPNET or NETWORK SERVICE user account.