Establish A Connection When The App Is Launched And Keep The Connection Open Until The App Is Closed?
May 20, 2010
I'm developing a device app in VB.net that will access a SQL Server database. I need to establish a connection when the app is launched, and keep the connection open until the app is closed. I've done the following:In the Master Module:
Public CNN
As SqlConnection
In the Main menu form load:
CNN =
New SqlConnection(sqlConnString)
CNN.Open()
Then when I want to read from the database:
Dim sqlDR
As SqlDataReader
SQL = "SELECT Name FROM Table"
[code]....
When I run the same code without the global CNN, but rather dim the connection inside the Select function, all works well.
I'm trying to insert a new records into database, one of those records is a "datetime"...when I type a wrong date, and try to insert those values into database, i get an error (about wrong typed date etc.)...ok, that's fine, things need to work that way. But here comes the problem, I correct the date, and then try to insert values again...here I get an error from the post title. And this doesn't work until I close that form and run it again...here's part of my code:
Dim cvLicence As New SQL Try cvLicence.upis("INSERT INTO blabla (itsnotimportant) VALUES ('something')") MsgBox("everything's fine", MsgBoxStyle.Information)
This will happen at random, and I can always just catch the error and re-establish connection to the server, but I am confused as to why. When doing lots of inserting into the sql server, I only establish one connection that is public, instead of many little connections. I had my doubts on a public sql connection, but it's been running great, and I've seen no problems until this morning. Again, this random moment I hit an error that stated, sql connection state is broken. Is it bad practice to just accept this error, and when it happens, re-establish the connection?
I have a simple scraper. It works on some websites, but on some there is this Error:
Quote:
IOException was unhandled Unable to read data from the transport connection: The connection was closed
It is occuring at "Dim htmlresults As String = Urlcontents.ReadToEnd()".
'Create the HttpWebRequest object Dim req As HttpWebRequest = WebRequest.Create(URL) 'Set the timeout to 1 second (or 1,000 milliseconds) req.Timeout = 10000
I'm using Visual Studio 2005 and SQL Server 2000 for my vb.net desktop application..I'm having a SQL Server exception saying that "connection can't be established to the server.hen connecting to SQL Server 2005 this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. Also showing
I just can't seem to establish a connection between my two P2P applications over the internet(LAN works perfectly fine).
I have tried the following. - Disabling Firewall - Changing Port
The only way I can establish a connection is if I'm connecting to the same computer using the universal IP or the local. Does anyone have a fix for this? Oh and here is the error that I receive when trying to connect over the internet:
System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it 255.255.255.255:8787 at System.Net.Sockets.TcpClient..ctor(String hostname, Int32 port) at P2P_Client.Form1.Msgtxt_KeyDown(Object sender, KeyEventArgs e) in C:\Users\Administrator\Documents\Visual Studio 2008\VB Projects\P2P-Client\P2P-Client\Form1.vb:line 32
i use vb 2008 office 2007 , it's a powerpoint add-in application. I need to use a window form as a bluetooth interface.the working procedure is like that when i click the Enum button, it will help me to search for available bluetooth devices.but now i have an error, it shows "WCL ERROR: Specified transfer is not available"
I have being trying without success to create a program that can establish a SSH connection with [URL] on a changeable post with a set username and password. The program when done will configure IE proxy settings and establish a SSH connection to [URL] to allow the user to browse the internet without restrictions.
I'm designing a web service in ASP.NET and VS2008, and am using typed datasets for retrieving table data. These work well and establish their own connections through their associated TableAdapter objects. Edit: I'm using VB, BTW!I am now attempting to run a custom SQL string using a DataAdapter and a Command object, however I need to reference a Connection object in order for the Command to work. What is the best way to handle this?hould I:a) Create a global connection object using Global.asax, retrieving the connection string from web.config? (I've been trying that one already, with not much success)b) Create a class-level connection object using the InitialiseComponent method, also retrieving the ConnectionString from web.config?c) Retrieve a Connection from one of the TableAdapters that I've already created in my typed DataSets?d) Something else I haven't thought of yet?
I want to start a new project on PC and Mobile Phone. But i'm still have so many question about the communication between PC and Mobile.
My project List: 1) My idea is establish a connection between PC and Mobile through IP address in first, but my question is 'How to do it' ? izit same like PC to PC by using Winsock open a port to access? i'm using VB.Net 2005 for PC and Net60 for mobile.
2)My mobile phone Nokia 6220 Symbian OS is support GPRS/3G. Since the GPRS/3G can connect to the internet, izit means mobile itself have a IP address and service provider in order to surf the web? So, can i connect my mobile phone to PC through this gateway?
i make a class and when i call on form then that error occurs "ExecuteNonQuery requires an open and available connection, the connection Current stat is close "
Class Code isImports System.Data.SqlClientImports System.DataImports System.StringPublic Class DatabaseKits Dim Cn As New SqlClient.SqlConnection Public Function BuildConnection() As Boolean Try Cn.ConnectionString = "Persist Security Info=False;Integrated Security=True;Trusted_Connection=Yes;database=BizAimsPro2008;server=Server-2k3s" BuildConnection =
I have a project in Visual Studio 2008 and there is a working data connection to a MySQL database. In other words, I can query the db directly from Visual Studio and it will display the results.
I've tried a couple of approaches that I found online for writing a connection string and accessing the db, but no luck yet.
All I'm trying to do is code a button to query the db and then reset the text property of a label/textbox to display the results based upon another label/textbox value.
The pseudo-code I am imagining is something like this:
Private Sub query_submit_button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles query_submit_button.Click result_textbox.Text = SELECT field FROM table WHERE otherfield = key_textbox.Text End Sub
I didn't see any related questions posted on SO - forgive me if I missed one that already exists and this is a dupe.
I am confused; I am using VB2010, IBM.iSeries.DB2 on an as400 V5R4. I am trying to establish an OLEDB connection, and return the values from the selected table to a DataGridView. I had one of the admin's make me file named GARBAGE, in the Rprtaccess catalog. In the past, I have been able to connect via access and an ODBC connection. My project is too big for access, and the SQL middleware we have is clunky and not user friendly. This is a program that will generate the SQL statements, specifically the WHERE: clause and populate the datagrid with the selected criteria. In essence I am making a user friendly striped down program, that has variables that are manipulated by the end user, and the rest, referenced tables and libraries are coded.
Imports System.Data.OleDb Imports System.Exception Public Class Form11
I am using the visual studio 2008 but use the guide for 2oo5 .I wonder why the program show error after click the load button (btnload). I am following the http: [URL] and having problem with the 'Filling the DataSet'. Is it because of different version?
The code I use: Public Class Form1 Private Sub Ordered_booksBindingNavigatorSaveItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Ordered_booksBindingNavigatorSaveItem.Click Me.Validate() Me.Ordered_booksBindingSource.EndEdit() [Code] .....
I have a problem connecting to an access database. I'm currently trying to build a login/register program that reads the username and password from a database and allows login if the specified username and password are found. I have code that will work properly for that so that's not an issue. However, when I make an attempt to register a new username along with a bunch of other things such as email, password, etc. I am unable to because the database connection is closed. The code I'm currently using to open the database connection is :
[code]...
However, when I try to use this code to open the connection to the database, it leaves the connectionstate closed. I decided to then build in as a test, a block of code that would check on load to see if the connectionstate is open or closed. Each time I've run it so far by making a few changes it always tells me that the connectionstate is closed no matter what I do.
I have create a simple app in vb.net that receive data from a bluetooth device ( data are simple strings like "90123.9mm"). Is there a way to check if the device has closed the connection ?
Im having 2 errors when loading the form the first one is: "The connection was not closed. The connection's current state is open" and the another one says "Conversion from string "" to type 'integer' is not valid" and everytime I change cmb_Suc appears: "The connection was not closed. The connection's current state is open" [Code]
I have a form that contains a crystal report viewer. When I open this form, it runs a report. I am using a .LDB viewer to tell who is logged into an access database. I noticed that when this form opens, the computer logs into the database and stays logged in. Even when the form is closed, the computer is listed as "logged in". If I run the report again, it just adds another instance of that same computer logged in. Therefore, it continues to pile up logins until the application is closed.
I have a fat VB.NET Winform client that is using the an old asmx style web service. Very often, when I perform query that takes a while or pass a large amt of data to a web service in a dataset, I get the subject error.The error seems to occur in < 1 min, which is far less than the web service timeout value that I have set or the timeout value on the ADO Command object that is performing the query within the web server.It seems to occur whenever I am performing a large query that expects to return a lot of rows or when I am sending up a large amount of data to the web service. For example, it just occurred when I was passing a large dataset to the web server:System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the rem
I have an application that copies a file from a network/internet location. I am trying to catch the exception for when the network connection becomes unavailable (or internet goes down). Currently i catch the exception "Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host." which occurs on the bold, underline line below.The issue i have is i try and attempt the operation to continue doing what it was doing by resetting variables and then reassigning them to continue reading the stream but cant get past this error. The only way to go past it is to stop and start the application which is not what im after. [code]
while looping through a short XML file called from xmltextreader retrieved from a webservice, I'm repeatedly getting the error: The request was aborted: The connection was closed unexpectedly. it constantly dies a row or two from completing the parsing.here's my short code:Code:
'Get the principal-id for Group Dim url As String = "https://xxxxx.acrobat.com/api/xml?action=principal-list&session=" & strCookie xmlRead = WebRequestToServer(url) Do While xmlRead.Read If xmlRead.NodeType = XmlNodeType.Element Then If xmlRead.Name = "principal" Then strGroupID = xmlRead.GetAttribute("principal-
