.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.
[code]...
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.
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?
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 = ""
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]
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.
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
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
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]
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
[code]....
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)?
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
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.
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...
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]....
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.
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)
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 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.
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."
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 = '" &
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
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.)
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
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] .....