I am creating a login form together with sql as may databse but when i run may program an error occur at "myData = myCommand.ExecuteReader()" stating that "Connection must be valid and open" what should i do on that to make it fix? [code]
View 7 RepliesI'm trying to insert data into a mysql database, I'm using xampp as well if thats of any relevance? I keep getting this error: Connection must be valid and open.
on cmd.ExecuteNonQuery()
I'm following my Microsoft Access application that I've also written as a reference and that works perfectly.' This is the code for inserting into an access database which works and is tryed and tested:
Imports System.Data.OleDb
Public Class frmEnterDetails
'text box variables
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I am building a program for a small office and I have a little problem with the code so I thought it's better to post a topic before continiue.. I have search into google and a lot of forums about database connectivity and my problem is simillar to other but a lot of things differs.The error that I get is on executeNoQuery() and it's called {"Connection must be valid and open."} Well a lot of things may related to about that.At least now from my re-search I covered all the filds of the problem and still not fixed. So please check my code for (Add new customer) button and let me know where I have mess up.
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Im clearly opening it there and its valid as i use the same connection to login with, anyone know the problem?
I'm trying to make a login from in vb2010 as a windows application but I keep getting a error message saying "Connection must be valid and open"My code for the sign in button is:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdok.Click
' Adminstration login
' Add code here for secure admin
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Here is code that I'm running. I am new to vb.net and setup a MySQL server 5.5 and I just want to insert a name into the database that is located on my computer. I can connect to it through the Server Explorer in Visual Studio 2010 premium, but when I try connecting in the program it gets to the cmd.ExecuteNonQuery() method and says that InvalidOperationException was unhandled. also I have the Connector/net version 6.45 installed
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i have an application. which is executed after every 5 mins. i have an open connection but it gives me the following error:
ExecuteScalar requires an open and available Connection. The connection's current state is closed.
my code is something like this. I have shown where all i am using ExceuteScalar()
Sub Main()
Try
connection.open()
cmd.ExecuteScalar()
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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 =
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Try If functionmode = "ADD" Then
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I got this error..The connection was not closed. The connection's current state is open.
This is coding to add data in Ms access in vb...
Imports System.Data.OleDb Public Class Form1
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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"
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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)
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Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
exitwithout()
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I have an VB.NET application. This Application is permanently resident in memory and minimized to the tray area because we use it very often. The problem comes in when we VPN into a client's site. These VPN connections trash all other network connections to and from our machines.Then every time my VB.NET application refreshes its database, errors start occurring, because the machine has lost connectivity to the SQL server, however, these are not at the connection level, but only when the reader attempts to read.
I am checking for connection.open, but because of the SQL connection pooling, I just get a previous connection that was valid before the network was cut. Is there anyway to check if an actual SQL connection is valid, prior to re-issuing a connection from the pool?[code]...
In my program, I have a timer with a inteval set to 1000ms. The timer is executing a MySQL-command, and right now I'm opening and closing the connection each time.
View 5 RepliesMVC3, VB.NET, using EF. I am working on coding up a simple function to handle checking for a valid MySQL connection. If the connection fails the test it will use the secondary server connection. This is required because our hosting provider does not provide failover or redundant MySQL servers. The problem is I tried to use a simple try catch method in the HomeController. This fails early because the Entity Framework is looking the connection that was set up when I set it up... Is there anyway to control that connection dynamically?
View 1 RepliesI was wondering if its possible for VB to display all available COM ports that are open. he reason that I ask this is because this program will be run on various computers where the COM port will not always be the same. I have a text box now that the user can choose which com number he/she wants but if the wrong one is entered, the program crashes rather than displaying an error message. It would also be nice for the system to show which available com numbers there are
View 5 RepliesI have a .mdf file that I open through an Open Dialog Box and use in a ConnectionStringBuilder (where I have the user instance set to True). Later, in one of my button clicks, I try to open the connection (connection.Open()). It then gives me an error as follows: "Generating user instances in SQL Server is disabled. Use sp_configure 'user instances enabled' to generate user instances."
Here is my code:
Option Strict On
Imports System.Data.SqlClient
Public Class frmMain
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I am currently working on a login page using vb.net. I would like to know how to make connection to an access database and verify that the user logged in is a valid user
View 6 RepliesI'm trying to connect to a database and keep the connection open for any amount of user activity/queries within the database. Currently I have a connection that opens and closes for any query (save, update, etc...) which requires the logon process to the back-end every time the user saves etc... Is there a way to simply connect and leave the connection open so there won't be a lag time when running the query due to the logon process? This is what I'm using:
Private sConStrFormat As String = "Provider=TDOLEDB;Data Source=TDDEV;Persist Security Info=True;User ID={0};Password={1};Default Database=bcpm_ddbo;Session Mode=ANSI;"
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i want to know how to open a connection to database from vb.net
View 3 RepliesI've been all over the help files and finally patched together a VB OleDb connection string for delimited text files:
Dim connection As String = "Provider=Microsoft.Jet.OLEDB.4.0;" & "Data Source=" & fName & ";" & "Extended Properties=""text;HDR=YES;FMT=Delimited"""
"fName" is passed in by an open file dialog.In every case (for all paths) it throws: 'C:1_2010NormalFileNormal.csv' (or where ever it is pointed) is not a valid path. Make sure that the path name is spelled correctly and that you are connected to the server on which the file resides.Since no path works, it must be a syntax error, but I'll be darned if I can see it.
Full code of this routine is:
Dim connection As String = "Provider=Microsoft.Jet.OLEDB.4.0;" & "Data Source=" & fName & ";" & "Extended Properties=""text;HDR=YES;FMT=Delimited"""
Dim conn As New OleDbConnection(connection)
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Are there any IP Address filters or masks available in Windows Forms as per following screenshot? A backslash shouldn't be allowed or it should be filtered somehow.
View 1 Repliesi am doin project using vb.net 2005 and using this sql query for connection
sql = "select username from login order by username"
con.ConnectionString = "Data Source=" & hostname & "; Initial Catalog=college;integrated security=sspi"
but m getting the following error:
Cannot open database "college" requested by the login. The login failed.Login failed for user 'CI4Admin'.
In our application we use IDataReader which actually call function from one.dll where weExecureDataReader()
We have many calls in application and in some places For some reason I am getting error message "DataReader already open" but I am not sure where.What will happend if I simple close that conection in the that .dll? Am I going to make trouble to database because one datareader left opened? I assume closing connection will close reader too and gargage collector will manage that left opened datareader..
SQL connections confuse me sometimes In almost every SQL related code on the internet the routine is like this;
* Open connection
* Execute SQL command
* Close connection
Is it good practice to just open a connection when the application starts and use that connection until the application closes?I know that sequential connections are required when processing more queries, but what if I need to poll a certain Table every x seconds? Isn't is better to keep that single connection open for as long as the application is running (and re-open when a failure occurs) instead of opening a new connection every x seconds?
Public Class app_mainform
Dim mssqluname As String
Dim mssqlpword As String
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I am developing an application that is using a Jet database (Access 2007). The database is local to the project (e.g., on the same drive and in the project directory). Any time I attempt to access the database (to create another DataSet, etc., via designer, etc.), I get the ubiquitous "Failed to open a connection to the database" with:
No error message available, result code: E_UNEXPECTED(0x8000FFFF).
Opening the Database Explorer and attempting to attach to the database results in the above as well. There are no apparent locks on the file, etc., and I'm the sole developer for this.
In the first form I will load Tabels in the secound I want to open the DB Connection. I wrote a Class which enables me to open and close the connection
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I'm trying to a open a connection to a local database and no matter what I try it just won't work (I'm pretty new to SQL Server and VB for that matter) I tried using 'sqlconnection' with different connection strings but none of them worked or gave me any useful error messages so I tried using 'OleDBConnection' instead, this hasn't worked either and it gives me this error instead:"A first chance exception of type 'System.NullReferenceException' occurred in MyProgram.exe"
Here is the code I am currently trying:
Private Sub MemDetailsSearch_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
ConnectionString = ("Provider = Microsoft.Jet.OLEDB.4.0;" & "Data Source = Database.sdf")
DataConnect = New OleDbConnection(ConnectionString)
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