SqlException：无法打开登录请求的数据库“ path \\ db.mdf”。 登录失败。 用户“ NT AUTHORITY \\ SYSTEM”的登录失败

Question

I know that this question have been already asked many times but I looked through the answers and haven't found solution for my problem.

I've built a Windows Service in C# that connects to the database and fill it with data from some other source. I set Account -> LocalSystem for ServiceProcessInstaller and StartType -> Automatic for ServiceInstaller .

I use Entity Framework to generate .edmx from database, this is a connection string:

<add name="ConStringName"
         connectionString="metadata=res://*/Model1.csdl|res://*/Model1.ssdl|res://*/Model1.msl;
     provider=System.Data.SqlClient;provider connection string='data source=(LocalDB)\v11.0;
     attachdbfilename=&quot;somePath\MyDbName.mdf&quot;;
     integrated security=True;connect timeout=30;
     MultipleActiveResultSets=True;
     App=EntityFramework'"
         providerName="System.Data.EntityClient" />

And I have this code:

var objContext = ((IObjectContextAdapter)dbContext).ObjectContext;
objContext.ExecuteStoreCommand("DELETE FROM Properties;");

On the second line I get

Cannot open database "path\DbName.MDF" requested by the login. The login failed.
Login failed for user 'NT AUTHORITY\SYSTEM'.

What I've tried so far:

1) tried this code for each database table:

GRANT SELECT, INSERT, UPDATE, DELETE ON  dbo.TableName TO "NT AUTHORITY\SYSTEM";

and without dbo.

 GRANT SELECT, INSERT, UPDATE, DELETE ON  TableName TO "NT AUTHORITY\SYSTEM";

2) I have set the permissions for this user 'NT AUTHORITY\\SYSTEM' in my database:
In SSMS: Databases => myDatabase -> Security -> Users -> 'NT AUTHORITY\\SYSTEM' -> Properties -> Membership -> db_owner

3) Tried to set perissions for this account in SQL Server: Databases -> Security -> Logins -> 'NT AUTHORITY\\SYSTEM' -> Properties -> set db_owner here

The weird thing: One time I have restarted the computer and everything was working!! Like this LocalSystem had permissions and the Windows Service could access the database and perform all the operations!

But than after some circumstances this exception started to appear again. I've tried to restart the computer but failed.

I know I'm missing something obvious. Please, help me find this thing.

Answer 1

Rather then trying to set permission to your database to local system account, it's better to do one of the following:

1. Change the account that runs the windows service to a Windows account that already have a permission in the database.

2. Don't use integrated security=True in your connection string but specify a User Id and Password .