IIS: ASP.NET не подключается с ошибкой "Failed to generate a user instance of SQL Server due to failure in retrieving the user's local application data path..."

If, when connecting from ASP.NET to MS SQL Server from IIS 7 on a server running Microsoft Windows Server 2008 (R2), the following error occurs:

Failed to generate a user instance of SQL Server due to failure in retrieving the user's local application data path. Please make sure the user has a local user profile on the computer. The connection will be closed.
The error usually occurs in the context of using SQL Server Express in conjunction with ASP.NET or other applications when a user instance of SQL Server is trying to be created, but the path to the user's local application data fails.

Possible causes and solutions to this problem:

Missing folder permissions: Ensure that users running the web application in the ASP.NET context have permissions to the application's local data folder.

Incorrect database connection settings: Check the database connection string in your ASP.NET application. Make sure it is configured correctly to connect to SQL Server Express.

Issues with SQL Server Express: Make sure SQL Server Express is installed and running on the server. Check its configuration and ensure that user instances are allowed.

SQL Server version conflict: Ensure that the version of SQL Server Express your application is using is compatible with the version specified in the connection string.

Problems with the user profile: Sometimes problems can be related to the user profile. Try creating a new user or updating your current user profile.

Check your security settings: Make sure ASP.NET has the necessary permissions to run the application and access local data.

Check IIS configuration settings: Sometimes the problem may be related to IIS configuration settings. Check your application pool settings to ensure they are configured correctly for your application and SQL Server Express.

You can also do the following:

1) Open the IIS snap-in (Start -> Administrative Tools -> IIS Service Manager)

2) Go to the "Application Pool"

3) Select the desired application and select “Advanced options” in the right panel

4) Go to the “Process Model” section and change the “Identity” option to “Network service” or to “Special account” (for the latter option you need to enter the username and password under which the application will run).

After this, the error should disappear.

Valid for: Windows Server 2008 R2; MS SQL Server 200x; IIS 7

If the problem remains unresolved, detailed event logs or error logs may provide additional information about the cause of the error.