When installing the SQL Server database, select "Windows Authentication Mode" for database operations in. net.

When the SQL Server database on the server is installed, the "Windows Authentication Mode" is selected. in the. NET database connection string, you cannot use the mode with user logon. the connection string in config can be written as "Data Source = .; initial catalog = Step1; Integrated Security = true ", this wayProgramError:
Database Error. Error cause: Unable to open the requested Database "Step1 ". Logon Failed. User 'nt Authority \ Network service' Login Failed.

Therefore, you must set the permissions of the 'nt Authority \ Network service' user. The specific steps are as follows:
Add the 'nt Authority \ Network service' user to the user of the "Step1" database in the resource manager of SQL Server2000 or management studio of SQL server2005, and tick "db_owner" in "role member.

This will allow normal access.