.net - WebClient.OpenRead Exception: "Value Cannot Be Null."?
Sep 23, 2010
I'm developing a scraper that scrapes one web page for links, then creates threads which execute scraping of subpages.
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I've noticed that sometimes (usually when there are more simultaneous threads running) a thread throws an exception. It happens randomly, the exception is thrown at client.OpenRead and it says "Value cannot be null. Parameter name: address". I also have a try..catch here so I put a breakpoint in the catch block and it appears that the _Address is valid at the time, yet the code throws an exception.
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Dec 15, 2011
I have a fairly simple piece of code:
Private _PurchaseDelivery as PurchaseDelivery
Protected Overrides Sub InsertItem(ByVal index As Integer, ByVal item As PurchaseDeliveryItem)
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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?
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Aug 12, 2009
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]....
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Mar 20, 2011
when doing the exact same thing on a diffrent pc it give me "An exception occurred during a webclient request." even in debugging.the first way is the regular "my.computer.download file" and the second one is:[code]
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Mar 18, 2011
I have a problem whit the webclient request. It work great on my pc, but my pc alone. It just says "an exeption occured during a webclient request." I thought it was the user-agent header.. but now when I have that, its the same.
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Oct 10, 2010
I have not much experience with the WebClient.. How can I catch this exception of e.Result DownloadDataCompletedEventArgs; "The remote name could not be resolved", which occurs after some time when internet connection is not working..? [URL]
The calling method:
Private Sub DoDownload()
Dim wc As New WebClient
Try
wc.DownloadDataAsync(New System.Uri(Me.webImageLink))
AddHandler wc.DownloadDataCompleted, AddressOf OnDownloadCompleted
Catch ex As Exception
Debug.Print(ex)
End Try
End Sub
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Oct 20, 2011
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
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Jun 27, 2012
visual basic application prompting me a message "Object reference not set to an instance of an object". i have 2 project in one solution. One is developed in c# and other is in vb. i am calling a method of c# project in vb project. the vb code is:[code]when i debug vb project individually it works properly and when i call vb application from c# application, it prompting error. is i missed out any .net framework reference? [code]
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Jul 26, 2011
My site has been running fine for sometime now until recently I see in the event viewer a null reference exception in the DNN core:
DotNetNuke.Common.Globals.GetStatus() in
F:BuildsMaintenanceWorkingDirectoryLibraryCommonGlobals.vb:line
1125 at DotNetNuke.Common.Initialize.InitializeApp(HttpApplication
app) in
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the line 1125 is:
_Status = UpgradeStatus.None
Which is a property of the Globals class and an Enum Also when this happens it doesnt just do it once then sort its self it does it roughly every minute for an hour or so.I made sure all dataprovider.instances are either in a using or a try catch finally or self closing(if the reader is not used)?
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Mar 7, 2011
I have the following code, which is meant to loop through a list of CheckBoxes and if checked if gets the text contained in the linked textbox through the tag of the Checkbox, i have used it before and it worked fine but this time i am getting the following error:
Null Reference Exception was unhandled
Dim DisCheckBox As CheckBox() = {chk0_6, chk6_12, chk12_18, chk18_24, chk2_3, chk3_4, chk4_5, chkXSB, chkSB, chkMB, chkLB, chkXLB, chkS, chkM, chkL, chkXL, chkXXL, chkXXXL, chkXXXXL, chkW8, chkW10, chkW12, chkW14, chkW16, chkW18, chkW20}
For Each Chk In DisCheckBox
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Jul 19, 2009
I keep getting a null reference exception w/this program, and its on the line that declares the array. I've looked it over and over and I just don't see why... Can you let me know if you see anything obvious? I'm also getting an "index out of range" exception, but it looks right to me...I declared everything with an 11 for 12 months, 0 to 11 for the intcount.
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Oct 23, 2009
If Not obj is Nothing and obj.IsActive Then ' null reference exception??constructions like this in C# works, because obj.IsActive is not checked if the first condition is false...
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Jun 7, 2010
I am building a VB.net application using VB Express 2008 which connects to a MySQL database. Right now, I am only selecting records, but will be writing code for update / insert. I have installed the MySQL Net Connector, most recent stable build. I have set a reference to it in project references. It makes a connection and reads just fine, no issues there at all.
My problem is this: When exiting the project (via calling "End") I am receiving a null Exception error. Here is the error[code]....
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May 4, 2009
I am using Windows Vista x64 + VSTS 2008. I am debugging the sample program from the following URL (associated sample code for this article),
http://www.codeproject.com/KB/audio-video/CaptureScreenAsVideo.aspx?display=PrintAll&fid=129831&df=90&mpp=25&noise=3&sort=Position&view=Quick&fr=101&select=1160633
But I met with null pointer exception when press the write to file button, here is my screen snapshot.
http://tinypic.com/view.php?pic=14cbfop&s=5
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Apr 4, 2011
i have this sql transaction i am using to make sales.But when ever i run the code it give me this null reference exception.I do not really know what is wrong.
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Sep 13, 2010
Now, when I try to debug my program, it immediately throws the exception below, this is before entering the program itself if I understand correctly. Any advice on how to resolve this? Between now and the last time I tried running debug, I had tried making a section of the program MDI, but gave up on that and delete that code. Also none of that part of the program is even in a position to be ran (the initial interface and onward do not execute that code)
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Feb 21, 2012
I'm currently taking a VB class and i'm having trouble running my program properly.[code]
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Jun 9, 2011
started learning vb.net..encountered this problem in this code: Private Sub NavigateRecords()
TextBox1.Text = ds.Tables("stdDataSet").Rows(inc).Item(0)-error msg appeared here sayin null reference evception was unhandled. Object reference not set to an instance of an object.
TextBox2.Text = ds.Tables("stdDataSet").Rows(inc).Item(1)
TextBox3.Text = ds.Tables("stdDataSet").Rows(inc).Item(2)
TextBox4.Text = ds.Tables("stdDataSet").Rows(inc).Item(3)
[Code]...
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Feb 10, 2010
write know i am gettin null reference exception due to followin code
Imports System.Xml
Imports System.IO
[code].....
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Jul 13, 2010
in the ReadFile() Sub, if the user tries to read a file that is not there he gets an exception
which results in the 2nd line in the Catch being executed. So far so good. But the 2nd line of
code in the mnuOpen_Click then gets a System.NullReferenceException which I don't understand since
the mnuOpen_Click code all works fine when called from the Open menu item. The exception
information suggests I use the "new" keyword to create an object instance, but in all my reading
and all the different ways I've applied the keyword New to the code, I've not been able to figure
out how to do this.[code...]
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Feb 4, 2011
i keep getting this null reference exception error and i can't figure out what i need to do to fix it. I have this in the form
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Mar 18, 2012
keep getting this null reference exception error and i can't figure out what i need to do to fix it.I have this in the form
Private Sub cbLookUp_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbLookUp.Click
Dim webDownload As New Net.WebClient
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Feb 15, 2011
Code will run from frmFacility and will shift into UserControl:
Public Class frmFacility
Private primaryBaseDay As Date
Private isClassPrimaryView As Boolean = False
[Code].....
At the line If facilityForm.IsOnPrimaryView Then, I get a NullReferenceException. Do you know the reason?
Also, I cannot create a new instance of the facilityForm, since I need to work with its singleton, although when I add a new instance of frmFacility, the IsOnPrimaryMode is set to false while it should be set to true in the gotoday sub from frmFacility.
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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."
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Jan 22, 2012
I'm using vb.net and sql server 2000 for developing my application....The problem i'm having is the Null Reference Exception on the Following line of code:
Dim cmd5 As New SqlCommand("select crtns_removed, pieces_removed, scheme from Outgoing_Invoice where invoice_no = '" & Me.ComboBox5.SelectedItem.ToString.Trim & "' And category = '" & Me.ComboBox1.SelectedItem.ToString.Trim & "' and item_name = '" &
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Apr 8, 2010
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Anyone know why, Every time I try calling something with this PhysicalAddress it says Null Exception, and the debug always displays nothing inside the Var's, Is this a bug or something? Im using Framework 2.0 >:O
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Jul 9, 2009
I am developing a twitter application but getting a null exception. when I searched indeep I found I am not getting any Users array from getTimeLine() Method.My user name and password are correct (The application is actually available on twitter API site.)
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Dec 14, 2009
Public Class Form1
Dim int As Integer = 0
Dim CustomerTable As New DataTable
Dim instance As New InvalidOperationException()
[code].....
This is the code this exception occurs when i click on the home button of my webbrowser.or i enter any site on the combobox.
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May 20, 2010
I am loading data from an excel sheet using the following code.The first test I did worked fine.But when I tried another sheet it errored on a cell that was blank"Object reference not set to an instance of an object".Even though the sheet in the first test had blank cells.I need the loop to load the blank cell in the datatable
For nRow = 1 To objSheet.UsedRange.Rows.Count - 1
dr = dt.NewRow
For nCol = 0 To objSheet.UsedRange.Columns.Count - 1
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Aug 5, 2011
I get a warning message that reads " Variable 'cust' is used before it has been assigned a value. A null reference exception could result at run time.", but it occurs in my vb file "Northwind.vb with the following code:
Public Class Northwind
Private cust As BizObjects1.Customer
Private Sub frmCustomer_Load( _
ByVal sender As System.Object, _
ByVal e As System.EventArgs) _
Handles MyBase.Load
[Code] .....
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