连接字符串导致用户在创建表时登录失败，但在创建数据库时没有

我已经能够用这个连接字符串创建一个新的数据库:

 SqlConnection myConn = new SqlConnection("Server=.''SQLEXPRESS;Integrated security=True;User Instance=True");

但是当我使用这个连接字符串创建一个Table时:

 SqlConnection connection = new SqlConnection("Server=.''SQLEXPRESS;Database='FormsDB';Integrated security=True;User Instance=True");

用户

登录失败

I tried so far:

SqlConnection connection = new SqlConnection(@"Server=.'SQLEXPRESS;Initial Catalog='FormsDB';Integrated security=True;User Instance=True;Trusted_Connection=True;");

和我得到相同的错误信息:

 System.Data.SqlClient.SqlException (0x80131904): Cannot open database "FormsDB" requested by the login. The login failed. Login failed for user 'LC-SURF'Tums'. at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) at .....

如有任何建议，不胜感激。

谢谢。

string ConnectionString = @"Data Source = .'SQLEXPRESS;Initial Catalog = FormsDB;Integrated Security = True; User Id = sa; Password = sql";