Combobox Giving 'DBNull' Error When The First Item Is Chosen
Oct 5, 2009
I am using combobox to populate values from a table, 'Suppliers'. I put this combobox in a form wherein the order details are filled up. This column 'Supplier' is a Foreign Key and set to NotNull in the order detail table. Selecting the first available entry on the combobox gives error 'SupplierID cant be Null' . Selecting the 2nd value is OK, first choosing 2nd and coming back to 1 is also OK. This error comes up when trying to update the database.Even with the first value, the combobox is having a text. I would like to know why the error.
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Jun 17, 2011
I am new to vb.net and I am using visual studio 2010. I have two comboboxes on a form, each combobox is set to DropDownList so that a list of items can show in the combobox, but no text is allowed to be entered.
For combobox A, if user chooses item 1, the list of combobox B should be updated accordingly. I think this is quite common on a lot of applications. But I do not know to implement it. I even do not know the keyword to search for the relevant property or event handler.
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Mar 3, 2012
When i select an item in my combobox it raises the following errorColumn 'field1, field2' is constrained to be unique. Value 'test1, 1' is already present.The combobox is bound to the table to populate it with values from field1 witch is the first part of primary key of the table. (field2 is secont part of primary key).
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Mar 1, 2012
The following code was taken from a javascript script. What it's (supposedly) doing is assigning properties to the line item. A name, a relations array, rounds array (which they lost in), total wins, three tiebreaker scores, and if they had a bye. (This is for a swiss pairing algorithm.)[code]I want to do something like this in Visual Basic. I'm pulling data from a table using a OleDBReader. I want to give each item that is pulled a set of these properties. Then by some means changing them.
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Apr 3, 2011
I have used the command:
For Each Proc as process in process.getprocesses
Combobox1.Items.Add(Proc.MainWindowTitle)
to populate a combo box with the list of current process windows, however for every process that doesnt have a main window title there is a blank space, is there a way that I could tell it to not insert the item if it's mainwindowtitle field is blank?
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Nov 9, 2011
I am receiving this error on this line
ctl.Value = CType(Me.Value, DateTime)
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Oct 31, 2009
Just started on vb.net
I have a combo box with "yes" and "no" with i select Yes i want the label2 to change the text to "yes" likewise with "no"
I've tried to code it in a logical way as possible but it just doesn't works except for the "wtf" so i think that overall my code is correct but the way i want to retrieve the selected item from combo box is wrong.
Public Class Form1
Dim aa As String
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
[Code].....
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Dec 29, 2011
i have a combobox containing countries name and their codes like INDIA:CNT001 then i have a textbox that store the code of country i.e CNT001(fetching from database) Now i want to match that code with the combobox code so that the combobox is set to that item when i click a button. i m using vb.net and sql server as database.
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Feb 13, 2011
my program downloads into a combobox every item(line) that is in a text file located on a server.
Every line in the text file ends with "a)" or with "g)".
Now I just want to make 3 radio buttons:
- one that will allow the download in the combobox only the item ending with "g)"
- one that will allow the download in the combobox only the item ending with "a)"
- one that will allow the download in the combobox of both (I already know how to do).
How can I do so?
To download the entire list in the combobox I do:
Dim List As String = client.DownloadString("http://mywebsite.com/mytextfile.txt)Dim lines As String() = List.Split(New String() {ControlChars.CrLf}, StringSplitOptions.RemoveEmptyEntries)ComboBox1.Items.Clear()
ComboBox1.Items.AddRange(lines)
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Jun 29, 2009
I am trying to connect to a remote machine through a vb.net application and want to retrieve the system information using WMI Classes. But the source line (scope.Connect()) as below generates an error "Access Denied HRESULT...." [code]
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Oct 26, 2006
I just finished putting the first 6 datagrid controls on my form and i went to go test it and got this build error: Error 4 Value of type 'String' cannot be converted to 'System. Windows.Forms.DataGridViewTextBoxColumn'.C:SoftwareForm1.vb 1425 19..When the line generating the error is this Me.Name = "Form1".where it has the "Form1" portion underlined in blue.This is a weird error because that line was made by the IDE to say the name of the form and has nothing to do with 'System.Windows.Forms.DataGridViewTextBoxColumn'.I tried saving my progress and restarting the IDE with no luck..Now I cannot even access the form in designer mode,One or more errors encountered while loading the designer. The errors are listed below. Some errors can be fixed by rebuilding your project, while others may require code changes.The designer cannot process the code at line 1424: Me.Name = "Form1" The code within the method 'InitializeComponent' is generated by the designer and should not be manually modified.
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Nov 9, 2011
I am recieving this error on this line
ctl.Value = CType(Me.Value, DateTime)
Conversion from type 'DBNull' to type 'Date' is not valid.
I am using Data Grid View and This is a calendar Type Column
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Nov 12, 2011
I've got the following LINQ Statement:
[code]...
invRecord.Pack_Num is a field of type Integer. This means that when I try to access it, if it is DBNull I get a StronglyTypedException. The above code throws this exception. If, however, I remove the "invRecord.Pack_Num = PSNum" and in its place put something like "True", the code works fine. So I guess my question is, why is that that invRecord.IsPack_NumNull() returns False when the value is in fact DBNull and what can I use as a conditional instead? I've been beating my head against the wall for a while now and I can't find a solution to this problem.
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Jun 5, 2010
Im trying to populate my Listview and im getting an DBNULL value error. Ive tried the following code but it doesnt work.
Me.SpMainSearchTableAdapter.Fill(Me.CapitalVisasCRMDataSet.spMainSearch, Me.tbxSearch.Text)
Me.lsvSearchResults.Items.Clear()
[Code].....
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Dec 10, 2011
It's saying I cant access this object in my class. Why? I'm pretty sure Ive used this method several times before. Below is some bits of code to figure this out. Object reference not set to an instance of an object."
[Code]...
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Jun 8, 2012
When I am scrolling datagrid after selecting one row I am getting error as "An unhandled exception of type 'System.StackOverflowException' occurred in System.Windows.Forms.dll" on line :
MyBase.Edit(source, rowNum, bounds, [readOnly], instantText, cellIsVisible)
Whole code is given below :
[Code].....
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May 17, 2012
I am trying to check to see if a value in a textbox is already in a drop down list. If it is, I will simply write to a label. If the textbox value is not in the dropdown list then I want it to write to the dropdownlist.
I am getting the following error Collection was modified; enumeration operation may not execute
HTML
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
For Each value In DropDownList1.Items
[Code]....
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Nov 11, 2009
I've written a new DAL and BLL, but when I try to create an instance of my class, I get an Object Reference error, is there anything particular I should be looking for? I am fairly new to this concept?
Call is such:Protected Sub btnSignin_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles btnSignin.Click Dim l As New Log()l.Log = "Attempted staff login with username [" & txtUsername.Text & "] and password [" & txtPassword.Text & "]"
[Code]...
Intellisense highlights no problems and if I Build the web site in VS I get a few warnings about schema information in the web.config (unrelated), otherwise no problem.
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Jun 29, 2009
Trying to run the following code but am receiving an string to integer error. Basically, I am running a report through code and trying to retrieve a number from a line of code by removing the line description and spaces. Having problems trying to figure out how to do that.
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim strURL As String
[Code].....
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Aug 18, 2009
I have a show button.The user will select a data from the dropdown list of the combo and on clicking the show button the corresponding data will be fetched from the database and will be shown in the corresponding fields.So I did this
Private Sub Show_Btn_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Show_Btn.Click
Using connection As New OleDbConnection("Provider=Microsoft.Jet.Oledb.4.0;Data Source=BankAccount.mdb")
connection.Open()
Dim command As New OleDbCommand("Select * from BankAccount", connection)
Dim reader As OleDbDataReader = command.ExecuteReader()
[Code]...
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Feb 18, 2011
Private Sub btnUpdate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnUpdate.Click
Me.Personal1TableAdapter1.Update(Me.HRDataSet4)
Dim myConnection As OleDbConnection
Dim myCommand As OleDbCommand
[Code] .....
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May 10, 2012
I use web methods in a couple of places in the intranet site im working on and they work fine, however one page is constantly throwing a HTTP 401 error every time I try access the web method.
Im not sure how to aproach this issue, I have tried commenting everything out of the web method, and still get the 401 error, even a basic connect to the database just doing SELECT 1 does not show up when I watch the DB with profiler.
My web.config is the same for all pages in the intranet and I cannot see any differences in my ASP.Net page compared to pages where web methods work.[code]...
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Jan 21, 2011
I've developed a windows service that connects to a database and executes a Stored Procedure when running in debug mode I get the following message: "ContextSwitchDeadlock was detectedMessage: The CLR has been unable to transition from COM context 0x1ffc20 to COM context 0x1ffd90 for 60 seconds. The thread that owns the destinationcontext/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations."
vb
'Explicitly imports a namespace into a page, making all classes and interfaces of the imported namespace available to the page.
[code]....
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Mar 24, 2009
I'm trying to trigger an animation declared in the window's XAML file from the window's vb code when an event is raised (calling a function), like a window's "loaded" event.
Here's how I declare the animation (as a storyboard):
Dim StartAnimation As Storyboard = DirectCast(FindName("ServiceOn"), Storyboard)
Dim StopAnimation As Storyboard = DirectCast(FindName("ServiceOff"), Storyboard)
And here's the code for the function that is failing:
[Code]...
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Apr 23, 2009
i want to scroll with my mousewheel from first item back to last item and scroll then scroll more back.to scroll up from last to first i have with the folowing code but how to do it backward i dont know.
Public Class Form1
Dim i As Integer
Private Sub ComboBox1_MouseWheel(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles ComboBox1.MouseWheel Try If ComboBox1.SelectedIndex = ComboBox1.Items.Count - 1 And e.Delta = -120
[code]....
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Apr 29, 2011
I am querying a datagridview and it works great unless one of the cells has nothing (dbnull). How to over come this?Exceptions: Operator '=' is not defined for type 'DBNull' and type 'DBNull'.
Dim query = From row As DataGridViewRow In DataGridView1.Rows _
Where row.Cells(SelectedColumnIndex).Value = filter _
And row.Visible = False _
Select row Distinct
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Mar 20, 2012
I have dates I am reading from a database, when I format the dates and there is a blank date I have a dbnull error...
What is the correct syntax to say
IF txtOrderDate = DBNull
then
txtOrderDate = ''
ElseIf
txtOrderDate <> DBNull (return the formatted date)
' Populate Header
[Code] .....
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Apr 22, 2012
I am creating a form that is able to update data in SQL server after selecting an MS Access file (.mdb). I am having an issue where the data has a single quote ('). I found out that the solution was to use Replace() - to replace the single quote with two single quotes - Replace(string, "'", "''").Now, for some reason, I am getting an error "Conversion from type DBNull to type String is not valid." Here is the code.
cmd = New SqlCommand("Update Child Set " & _
"TopLevelProject = '" & row("TopLevelProject") & "' ," & _
[code].....
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Jun 9, 2010
** Edit - just thinking - I have this export code elsewhere in my application; testing it with blanks works fine. All the fields in the two forms are text fields. The only difference that I can see is that the form that is causing me a problem is based on a left join query from my database; the form that works is based on a flat table. Any ideas???
I have tried everything in my (very, very limited) knowledgebase for VB and am completely stumped. I'm sure the fix is simple, but no clue where to go. (I got this code from a site which I didn't make a note of, and cannot find it by doing a google search)...
The code listed below is supposed to export a datagrid view to CSV. It works fine - if, and only if - all the fields are populated. If one of my columns is blank, then I get a ""Conversion from type 'DBNull' to type 'String' is not valid." error. **Edited to provide exact error message
The code that's giving me a problem is the second IIf(intRowData < intColumnCount, strDelimiter, "").
[Code]...
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Aug 19, 2009
I've developed a small HR program that connects to the SQL database which is on the local PC. I've created an ODBC connection to connect to this server and the program works fine. I've used VB 2008 Express edition to develop.
My concern is now I want to install this EXE on a server. ON the server, I've created the same databses and successfully created an ODBC connection on the server as well. Also created one shared folder. I copied all my EXEs and DLLS on to this folder. On the server I was able to execute the program without any problem.
From a remote client, I opened this shared folder and try to execute and it was giving me an ODBC related error, basically it was not able to detect the SQL connection.What I want to achieve is to have one EXE. The program did not throw any other errors.
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