Connection String To SQL Server 2005 Express Database

Hi, all. I am using VS.NET 2005 and SQL Server 2005 Express. I tried to use the following code to connect to a database named "AMSPROD" that I attached to SQL Server 2005 Express:

 dbConn = new OleDbConnection(Data Source=.SQLEXPRESS;AttachDbFilename="C:Program FilesMicrosoft SQL ServerMSSQL.1MSSQLDataAMSPROD_Data.MDF";Integrated Security=True;Connect Timeout=30;User Instance=True);

dbConn.Open();

I got an error asking for provider with the above connection string, then I changed the conncection string to be like follows:

Data Source=.SQLEXPRESS;AttachDbFilename="C:Program FilesMicrosoft SQL ServerMSSQL.1MSSQLDataAMSPROD_Data.MDF";Provider=SQLNCLI;Integrated Security=True;Connect Timeout=30;User Instance=True

I got error: No error message available, result code: DB_E_ERRORSOCCURRED(0x80040E21)

Then I changed the Provider to be like: Provider=SQLOLEDB, now I am getting the following error:

Message: "Invalid authorization specification
Invalid connection string attribute"

Source: "Microsoft SQL Native Client"

StackTrace: " at System.Data.OleDb.OleDbConnectionInternal..ctor(OleDbConnectionString constr, OleDbConnection connection)
at System.Data.OleDb.OleDbConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningObject)
at System.Data.ProviderBase.DbConnectionFactory.CreateNonPooledConnection(DbConnection owningConnection, DbConnectionPoolGroup poolGroup)
at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
at System.Data.OleDb.OleDbConnection.Open()
at ISESAMSData.DbConnections.MakeConnection() in C:\ISES\ISESCommon\ISESAMSData\DbConnections.cs:line 74"

TargetSite: {Void .ctor(System.Data.OleDb.OleDbConnectionString, System.Data.OleDb.OleDbConnection)}

Strange thing is, when I use the Connect To Database under Tool menu of VS.NET 2005, I could make the connection to this database. Then I copied this connection string to the code, the connection couln't be made. I feel very confused.

I am wondering if I need to add ASP.NET user to SQLExpress. But I don't know how to do it?

Can anyone please help me out! Many thanks!