Disconnecting from SqlServer Database from VB.net

edmonson

Hello, I'am developing an App that needs to access a SqlDataBase named "Work", but this may be located in any drive of my system (C:,D:,U:,...). The database structure is always the same, so I use a unique name and only change the files. When the application start, I use a OpenFileDialog to locate the database and execute an storedprocedure to attach the database to SqlServer (EXEC sp_attach_db @dbname ...). This works fine, and I can work with the database. When the user ends to work with database, I want to detach ("EXEC sp_detach_db) this from my App to allow to choose another location one. At this point I get an error reporting that the database is currently in use, ans so, it can't be detached. StoredProcedures form attach and detach owns to Master database, so when I execute it I'am not using my database. Do you know any procedure to disconnect my App from database using system.data, and then I could execute the detach procedure ? (If I only execute Attach and Detach, without accessing to database, is runs fine). Here the Detach function:

Public Function DetachDB(ByVal DbName As String) As Boolean
Dim Cmd As New SqlClient.SqlCommand
Dim AffectedRows As Int32
Dim TmpDbName As String = _DbName
_DbName = "Master"
Cmd.Connection = GetConnection
Cmd.CommandText = "EXEC sp_detach_db @dbname = '" & DbName & "'"
Cmd.CommandType = CommandType.Text
Cmd.Connection.Open()
Try
AffectedRows = Cmd.ExecuteNonQuery()
Cmd.Connection.Close()
_DbName = TmpDbName
Return (True)
Catch e As Exception
If PopupErrors Then
MessageBox.Show("[DB]Error separando la base de datos " + e.Message)
End If
Cmd.Connection.Close()
_DbName = TmpDbName
Return False
Exit Function
End Try
End Function

Lost User

How does your connection-string look? Do you connect to the "master" database on the server, or to your named database?

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edmonson

The connection to the app database is:

"Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=work;Data Source=pcjordi2009\sqlexpress"

And when I connect to detach/attach I use:

"Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=Master;Data Source=pcjordi2009\sqlexpress"

Lost User

Looks good. Just tried from SQL Management Studio, one can simulate an open connection by simply opening a table in edit-mode.

ALTER DATABASE [AdventureWorks] SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
GO
USE master;
GO
sp_detach_db 'AdventureWorks';

The first command sets the database to single-user mode, effectively disconnecting everyone else :)

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edmonson

I've tested from Management Studio and it works properly. From my application, the problem continues. When I execute ALTER DATABASE... the DB enters in Single User Mode (An icon appears on Db List in Mabagement Studio, but when execute detach it fails reporting that Database is in use :(

Lost User

edmonson wrote:

When I execute ALTER DATABASE... the DB enters in Single User Mode (An icon appears on Db List in Mabagement Studio, but when execute detach it fails reporting that Database is in use :(

Strange.. Can you post the offending code here? I've tried it here this way, just to verify that it's actually possible;

string cs = "Server=.\\SQLEXPRESS;Database=master;Trusted_Connection=True;";
using (var con = new SqlConnection(cs))
using (var cmd = new SqlCommand())
{
con.Open();
cmd.Connection = con;
cmd.CommandText = @"ALTER DATABASE [AdventureWorks] SET SINGLE_USER WITH ROLLBACK IMMEDIATE;";
cmd.ExecuteNonQuery();
cmd.CommandText = @"sp_detach_db 'AdventureWorks';";
cmd.ExecuteNonQuery();
}

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edmonson

Sure, this code works and the database is deatached succesful! but when I execute an attach again: - Database is attached successful (I can see on Management Studio) - I open a connection an it opens succesful. - But when I call an cmd.ExecuteReader to get data, then next error message appears: "Error at level transport when send the query to the server. (provider: Shared Memory Provider, error: 0 - No process is on the other end of the pipe)" I've reviewed SQL configuration, and all seems good. If I restart the App all work succesful. Any idea, why the server process stopped ??

Lost User

edmonson wrote:

Any idea, why the server process stopped ??

Alas, no. Is it replicatable?

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edmonson

Sorry, the message was: Sure, your code works and the database is deatached succesful! but when I execute an attach again(the same database): - Database is attached successful (I can see on Management Studio) - I open a connection an it opens succesful. - But when I call an cmd.ExecuteReader to get data, then next error message appears: "Error at level transport when send the query to the server. (provider: Shared Memory Provider, error: 0 - No process is on the other end of the pipe)" I've reviewed SQL configuration, and all seems good. If I restart the App all work succesful. Any idea about it ?

Lost User

I don't know; does it happen every time after a reattach?

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edmonson

Yes, every time I attached again (without exiting from application) and try to get data, the problem appears. But if I restart application and reattach then works fine ! (Strange behavior:-() If I find the solution I'll report it.

Lost User

edmonson wrote:

Yes, every time I attached again (without exiting from application) and try to get data, the problem appears.

Without exiting from the application; so something gets left behind, in either the application or SQL Server. When the application starts to fetch data, then the application will create a new Connection object, right? Thinking out loud; the database is re-attached, from within the application. Could it be that we disconnected an active DataReader during the detaching?

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