Developing a simple app in vbe 2010. Suddenly I have a (fatal?) warning ("Value cannot be null. Parameter name: object Type") and can no longer access the form. Problem seems to have started when I laid a timer down. Have since commented out the timer sub and call, but the warning persists. I can, strangely, run the app in debug. Have carefully inspected the all code and came fine no error.
View 3 RepliesI am trying to utilize the access database, but I'm getting an error message: Value cannot be null. Parameter name: dataSet
[Code]...
That's the code I'm using, why I'm getting this error?
I want to add a null binary field in Database.[code]...
View 2 RepliesConsidering that Grade.firstExam, Grade.secondExam, and Grade.finalExam are all TEXT and not numbers, i can't get the exact solution to convert null values into Zeros. I already tried to use NZ() but it returns an error message (Undefined Function 'NZ' in expression)im using VB.net with MS Access as my database. i also imported System.Data.OleDb Namespace.
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How can i convert empty string or null that exist in the field?
I have tried to import an Access Request in Excel. However, the last field (SP) contains Null cells and it seems that it prevents the importation in Excel. There is a way to change Null cells?
Sub Creating_Universe()
Dim connFI As ADODB.Connection
Dim rs As ADODB.Recordset
[Code]....
I have a couple of textfields in a Windows form. One of these textfields is allowed to be NULL. When I enter a value for every field, it is all inserted, no problem. When I leave the field (txtGewicht) blank, I can't seem to be able to insert NULL in Access Database.
If Double.TryParse(txtGewicht.Text, 0) Then
klant.Gewicht = Double.Parse(txtGewicht.Text)
Else
[Code]....
This is what I get:
"Cannot set column 'Gewicht' to NULL, please use DBNull instead"
So I changed 'Nothing' to DBNull.value, but it then tells me that System.DBNull cannot be converted to type Double.
I have a button 'start quiz' which uses the dataset to fill the quiz form - ready for the user to start answering the questions.However, I am getting a 'null reference' at the point where the 'navigate records' on the quiz form is called. Have looked up that it means I have a variable that is null. But I have declared all the variables etc. Not sure what I'm doing wrong. I am very new to programming and I have spent quite a bit of time on this already.This is the code for the student user login:
Private Sub btnLoginStudent_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLoginStudent.Click
FrmQuiz.Show()
[code].....
How update the Access database in VB.Net with NULL values using OLE DB command
View 2 RepliesDid anyone knows where can I upload a folder so my programe to be able to download an update from there???
View 3 RepliesI have a select statement which was returning the required values but when I changed the OS date from English(US) to English(UK), it now returns null. I believe the problem is concerned with date since in the query am selecting values where the date from the database is the same as the date in a combobox but I don't know what else I can do. It almost looks like the dates in the combox and in the database are not the same and yet the date in the combobox is actually retrieved from the database and has been returning values fine until I changed the system date format.Here's my select command:
cmd4.CommandText = _
"SELECT sum(brought_qtty), recieved_qtty from brought_coffee, centre_weigh where brought_date=#" & _
dtComb.Text.Trim & "#" & _[code].......
i am working in windows appl vb.net 08. And i am working in Access DataBase.I have one Table Called "Person" . In this "Person" Table one Column Name Called "OtherName". In this Column binded in one of the Combobox in a Form.But the Problem is "OtherName" Column having the Null Values.Before i bind this Column to Combobox i want to convert this NULL Values to String. Why i need the values in STRING means , In my code i using this Combobox as a filter in SQL Query.If i didn`t change the Null Value to STRING , The Combobox SelectedText or SelectedValue is Showing Nothing. So i am not able to get the Record.
Whn i write a Sql Query to Combobox and apply filter in WHERE statement like Combobox.Selectedtext or Combobox.SelectedValue In "Selected Change Committed Event" then i should get the record in the Output right but unfortunatly i am not getting the Record. The Record Count in DebugPrint showing 0.
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I have a form and stored procedure that inserts the data from the form. It works fine except that if a field isn't filled in it doesn't insert a NULL into SQL it inserts "".
I've tried a few different ways but none seem to insert NULL, the one below still inserts "", can anyone point me in the right direction?
Here is the required part of the code, if you require more just let me know.
Dim rdr As SqlDataReader
Dim cmdInsert As SqlCommand = New SqlCommand()
cmdInsert.CommandText = "spPersonalDetailsInsert"
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So if I enter nothing into address1 field it should write NULL to screen but it always writes NOT NULL. What does an empty form field equal? in classic ASP it was always "".
I tried binding data to combobox at the runtime in the form load event. I had written the following bind function,
Private Sub BindComboBox()
Dim da As SqlDataAdapter
Dim conn As SqlConnection
Dim ds As DataSet = Nothing
[code]....
The problem is cboSubject.SelectedText is returning empty string.
I have a fairly simple piece of code:
Private _PurchaseDelivery as PurchaseDelivery
Protected Overrides Sub InsertItem(ByVal index As Integer, ByVal item As PurchaseDeliveryItem)
[Code]....
Which is inside a class which overrides a custom list base. The code is occassionaly throwing an unhandled exception, System.NullReferenceException, on this line when used in production:
If _PurchaseDelivery IsNot Nothing AndAlso _PurchaseDelivery.DefaultSKUBinID.HasValue Then
DeafultSKUBinID is declared as an Integer? (Nullable Int) in the PurchaseDelivery class. I cannot see what might be causing this error, why would this be returning an error?
How to check whether a column is null i use the following code but I got this error "Input string was not in a correct format."
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When I put a break point to the last if clause in the sub ("If (backOrder < 0) Then", see below) it runs until the break point, if I put the break point further below, I get the following error:
Cannot insert the value NULL into column 'OrderID', table 'WHM.dbo.OrderDetails'; column does not allow nulls. INSERT fails. The statement has been terminated.
I've discovered first hand that it only happens when prodqty is bigger then qtyOnStock, thus executing the if clause.
The code:
Private Sub NCOSubmit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles NCOSubmit.Click
Dim sqlText As String = ""
[Code]....
I'm writing an asp.net page with a simple registration form that connects to my access database and inserts the values in the table. So I have my database, my registration page, everything looks fine in my code, but there's a syntax error I can't seem to figure out. When I go on my webpage and click submit, it says : Syntax error in INSERT INTO instruction.
Here's my code:
<%@Page language="vb" explicit="true" debug="true"%>
<%@Import Namespace="System.Data"%>
<%@Import Namespace="System.Data.OleDb"%>
[CODE]...
I'm trying to insert data from an Access unbounds form to an Access Table using the follwoing code:
View 2 Replies[code]
Imports System.Data.OleDb
Imports System.Data.SqlClient
Imports System.Configuration
[code]....
I don't know if these can connect with Access, anyway, I got ERROR on the com.Connection.Open()?
I am trying to create a treeview in VB.net, the data has to be loaded from MSAccess 2010 database. When I try to run this program I get error : Argument Null Exception was unhandled, 'column' argument cannot be null and the program crashes. I have pasted the code as under:
Imports System.Data.OleDb
Public Class frmRating
Private Sub frmRating_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles
[code].....
In my window application, Form1 variable eg. Public str as string. value blank/null when move to Form2 and Back to Form1. How to maintain Form1 varable's value when back to Form1 In vb.net if any one know, reply me soon
View 2 RepliesI have 2 forms main_frm and copying_frm. In main_frm, there is a list view that is populated with file names. The user then clicks save and all the files in the list are copied to a folder that they choose using a folder browser dialog. When this happens, I do copying_frm.ShowDialog() to display the copying_frm. The copying_frm contains a progress bar and a cancel button. I can get the progress bar to indicate how much has been copied. But that freezes up the application. To get around this, I create a new thread (called copyingThread) that copies the files. When that thread runs though, it can't access the waitingList_lvw in main_frm. For example, in the function that the copyingThread executes, if I have this line of code: MsgBox(main_frm.waitingList_lvw.Items.Count.ToString()) the result is 0. Also, I don't get any errors and no files are copied. How do I access waitingList_lvw in main_frm from a thread called copyThread that was created in copying_frm?
View 6 RepliesCommunication between form can be done in many ways using constructor using delegates etc in .net but my question is how can i access a value that is entered into a child form from a parent form or can a two way communication is possible between windows forms.
View 1 RepliesHow to display contents of ms access database form on a form using vb .net...in visual studio
View 7 RepliesWhat is the best way to access a value of a control within a form outside of the form class. I have a lot of functions defined in a module, one of these functions requires a series of values from controls in my main form such as the FolderBrowserDialog.SelectedPath element. I understand that these cannot be accessed in the format form.FolderBrowserDialog1.SelectedPath and that they need to be accessed using a delegate. This is the part I am stuck with.
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I have designed my app for multiple gridviews. When a user double clicks a row it opens up the data in a modal form and when they commit changes the row gets updated.While they have that modal window open they can not go back to the grid.But I have a alerts/messages window always running (like outlook tasks). As soon as I open the modal window I can not access that tasks window. (Default behaviour)How can I open the modal form and still let the user access/view the tasks window while they work on the modal window.(I tried creating it in a differant thread, but got a lot of cross thread errors so decided to abandon that approach.I thought that 2 modal form can run at the same time as long as they have differant parents. But aparently the main GUI thread pauses as soon as you open a modal window on it.
View 10 Repliesbelow i have the form which i made in access, its BIG, REALLY BIGI am going to try and recreate this form using VB and MySQL, the question is how?The purpose of this form is to display all locations ready for someone to enter in information into them, normally the first field in each table has a unique name (which is set as the default value for that field), in the morning, the only field which is altered is a sign on field, which in access, the user clicks and the time is entered.
View 7 RepliesI have some code which gets child items for a menu via the GetChildren function which takes a list of menuData: Dim builtMenu As New List(Of MenuData)(_rawData.FindAll(Function(item) item.GroupingID = 0))
For Each menuData As MenuData In builtMenu
If menuData.Children IsNot Nothing Then
menuData.Children.AddRange(GetChildren(menuData))
End If
Next
If I check if menudata.children isnot nothing, it always is nothing because the GetChildren function is yet to run (providing the child items, which do exist). If I remove this check and just have this code:
Dim builtMenu As New List(Of MenuData)(_rawData.FindAll(Function(item) item.GroupingID = 0))
For Each menuData As MenuData In builtMenu
menuData.Children.AddRange(GetChildren(menuData))
Next
Then I am presented with a Object reference not set to an instance of an object error on menuData.Children.AddRange(GetChildren(menuData))
I have created a calendar in VB which works fine when set to the startup form, but when I use the MdiParent form as the startup form and try to display the calendar by use of a control it just shows all the buttons and labels with no values assigned to them. Its almost as if the Calendar_Load event is not working, or not accessing the methods in my CalendarClass.
View 2 RepliesI have two forms (fMain,fOptions)fMain is the main form with tabs created by a sub (createTabs())taking values from database fOptions is the options form where I change some numbers and values in the databasefOptions is called as ShowdialogIn fOptions I have a button (btnApply) to apply the changes to the database (it works -I've tested itI want to click on that button and refresh my tabs in fMain
View 7 Replies