.NET Inheritance With Collections "Object Reference Not Set..." Errors?
Nov 7, 2010
I am constructing a collection of objects, and need to use inheritance on a base class - I have been trying for hours in various ways and can't get this to work whatsoever - the error is always "Object reference not set to an instance of an object." The idea in the example below is that an object is instantiated, and within that lies a collection of Students when I try to access the oDemo.Students(0).Name property the error is raised. Otherwise the object appears to have instantiated OK.Here is the code being used to instantiate and access the class (from ASP.NET).
Dim oDemo As New MyDemo.Students
lblTest.Text = oDemo.Student(0).Name
Here is the sample code from the class library:
[code]......
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Aug 23, 2011
im sure it is something really simple. Im by no means comfortable with VB. The below code is not mine but i have altered it for my needs. However im getting a couple of errors.
Reference to a non-shared member requires an object reference. I have underlined the errors in the code and they all refer to the above description
[Code]...
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Jul 7, 2010
I have an "Object reference not set to an instance of an object" error that does not make any sense.I have a form with 2 datagrid views, (dgv1) and (dgv2).During the form load, I load the data for dgv1 and dgv2 without any problems. After the form load is complete, I get an error on the follwoing code.
[Code]...
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Aug 24, 2009
I have a parent class and many children class, right now it look like this:
Public Class Parent
Public Property ID as String
End Class
[Code].....
What I need is a strongly type list List(Of Child) that Inherits from ListOfParent (I need the FindByID method) but I can't find the right syntax.
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Sep 21, 2011
I am planning to use a List in my application but when I was searching for System.Collections.Generic, it only has System.Collections. I tried to look it up in the "add reference" and its not there.
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Mar 23, 2011
I have two custom objects.On of them inherits the other one, appends few more properties and methods, ovverides some other.When I try to cast the Parnet Object to Child I receive an error that it could`nt be done.
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Jul 30, 2009
I have an class named Foo. This class contains a collection of child objects of type FooChildBase, but I also have a further class of type FooChildTwo which inherits from FooChildBase.
Class Foo
Public Children As IList(Of FooChildBase)
End Class
Class FooChildBase
[code]....
What I would like to do is have my FooSpecial Class treat it's Children collection as if they were FooChildSpecial objects, but still be able to add FooChildTwo objects to it. Is this possible and if so how can it be done?
EDIT:I need to FooChildSpecial class to wrap any of the objects in the Children collection with the extra values, whether they are FooChildBase or FooChildTwo?
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Mar 17, 2012
The book "Beginning ASP .NET 4 in VB 2010" contains the following:NOTE: TaxableProduct inherits from Product.You can also cast in the reverse directionfor example, cast a Productreference to a TaxableProduct reference. The trick here is that this
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Sep 20, 2010
I have a question specifically about getting the current cookies set to a particular visitor on an ASP.NET webpage. I understand you need to use Request.Cookies - and by default it returns a collection of all cookies set, as an HTTPCookieCollection. However, the MSDN documentation states that you do: Request.Cookies("Username") as an example, in order to fetch an individual cookie and then compare whether it is set, etc. All fine and dandy but why adding parentheses and a string does the type suddenly change to
HTTPCookie.
I understand HTTPCookie is for dealing with individual cookies and HTTPCookieCollection is for dealing with multiple cookies at a time for like iteration purposes, etc., but I don't understand when on the MSDN documentation it explicitly states that the Request.Cookies property (the Cookies property) is of type HTTPCookieCollection, and if you do what I explained it changes the type (I can see this from IntelliSense) and it does not state this happens in the MSDN documentation. I'm not asking about the MSDN documentation lol, but why this happens when adding the parentheses and a string denoting the cookie name. I'm still pretty new to Visual Basic. By the way, I'm doing this all in Visual Web Developer although using VB as the language of choice.
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Jan 3, 2012
given the following class structures:[code]I add the following property to MyList, trying to answer questions like "find out the number of elements with specified type, say Derived1, inside MyList?"[code]
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Feb 24, 2009
is there any collection in vb.net which store object as byref and not byval.
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Aug 26, 2011
I have this bit of code
Private Sub SpellChkMenuItem_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles SpellChkMenuItem.Click
Dim activeRichTextBox = TryCast(Me.ActiveControl, RichTextBox)
'clsFS.CheckSpelling(activeRichTextBox)[code]....
When I am in the rtb and click on spell check button it tells me the error "Object reference not set to an instance of an object." On this line
SpellChecker.Text = activeRichTextBox.Text
But it is suppose to be getting the focused rtb correct? So why is it not referenced
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Mar 8, 2010
Can you define this :
Class
Object
Inheritance
Polymorphism
Abstraction
And could you make it easy to understand I'm having a hard time to understand those terms.
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Jun 29, 2010
I have been learning vb.net for about 6 months now and I red few books about basic visual programming as most to them have information about the basic concepts like what is Object oriented programming, subroutines, functions ,inheritance etc and bit about ADO connectivity to database. Having said all that I think I have good concepts about all these things but now I want to proceed further but can't find appropriate text books or online tutorials.
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Mar 15, 2007
My colleague and I have recently upgraded our projects from .NET Framework 1.0 and VS2002 to .NET Framework 2.0 and VS2005. We also applied the latest VS2005 service pack.
Our problem: normally when debugging we use the QuickWatch window to drill down into and view collections of objects belonging to the parent object we are "watching". THIS NO LONGER WORKS...instead, we get a message in the value line against the object collection saying:"In order to evaluate an indexed property, the property must be qualified and the arguments must be explicitly supplied by the user."This is incredibly frustrating, particularly when we have large nested collections of objects.We are pretty sure this feature was working fine after we upgraded, but we are not so sure that it was working after we applied the VS2005 service pack.
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Apr 25, 2009
I have a VB.NET project where I am able to iterate through the keys and values collections of a dictionary object using an index:
MyDictionary.Keys(idx)
MyDictionary.Values(idx)
When this code is taken from the test project and placed into the real project I get the following error:
'System.Collections.Generic.Dictionary(Of Double, String).KeyCollection' cannot be indexed because it has no default property.[code]...
In the line in sub search that says "dtf.Keys(idx) = 0" place your cursor after the right parenthesis and backspace you should get a tooltip that says, "<Extension> ElementAtOrDefault(index as Integer) as Double - index: the zero based element of the index to retrieve.
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May 6, 2010
Say I have a text file I want to load it to a System.Collections.Specialized.StringCollection
object dim a as System.Collections.Specialized.StringCollection
set a = a contains many systems System.Collections.Specialized.StringCollection object.
Each line in text.txt go to an element in a.
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Nov 28, 2010
I am receiving this error: Reference to a non-shared member requires an object reference on the code I've
bolded within the code body. Here is my code:
[Code]...
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May 8, 2010
I get this error:Reference to a non-shared member requires an object reference.When i compile on the following code section:
Private Sub statusBarToolStripMenuItem_Click(ByVal sender As Object, ByVal e As EventArgs)
ToolStripMenuItem.Checked = Not ToolStripMenuItem.Checked
statusStrip1.Visible = ToolStripMenuItem.Checked
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Jun 20, 2011
when I do something like this: Process.Start [URL] it says that error only on Form2 not Form1.
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Jul 23, 2009
Error 'Reference to a non-shared member requires an object reference'?I want to know what a non-shared member is.
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Dec 7, 2010
I am opening frmB (variable for FormB - the actual form) from frmA. From btn1 I open frmB like this:
frmB = New FormB()
frmB.Show()
From btn2 (frmB is already open) I bring frmB to the front from behind frmA:
FormB.Show()
FormB.BringToFront().
No problem so far. Now I need to pass an arg to frmB. This is where I am having the problem.
from btn1 (in frmA) I do this:
frmB = New FormB(myArg) '--pass myArg to constructor of FormB -- no problem here
frmB.Show()
then from btn2 -- this is where I have the problem
FormB.Show()
FormB.BringToFront()
I tried placing myArg in FormB.Show(myArg) but that did not fix the problem. What is the correct way to pass myArg to FormB (frmB) in this scenario? Do I need to share FormB or frmB? How do I do this? "frmB" is frmA level variable.
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Sep 22, 2009
why i am getting an "reference to a non-shared member requires an object reference" error on format.Yesterday gets the previous days date and presents it in a yyyyMMdd format.vsettlementDates takes the "Yesterday value and requests data from it.
Dim Yesterday As String = format(Today.AddDays(-1), "yyyyMMdd")
Dim vSettlementDates As String = (Yesterday)
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Apr 27, 2011
I am getting the following error:
Error 1 Reference to a non-shared member requires an object reference. (on WindowsIdentity.Groups)
Here's my code from that uses the WindowsIdentity.Groups property to display the identity references for the groups the current user belongs to. This code is part of a larger example provided for the WindowsIdentity class.
Public ReadOnly Property Groups As IdentityReferenceCollection
Get
Dim irc As IdentityReferenceCollection
[Code].....
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Dec 13, 2009
" GridView1.datasource = _MyUsers.Reference to a non-shared member requires an object reference." error. WHat's wrong with this code
<%@ Page Language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
[code]......
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Jul 22, 2011
I have the following code below, how the line where it says : For Each c As councillor In councillorList i get the error: reference to a non shared member requires an object reference. Can someone please advise where i am going wrong? [Code]
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Apr 6, 2012
Alright, so im getting this error:Reference to a non-shared member requires an object reference.This is the bit of code the error is pointing to:My.Settings.Bookmarks.Add(WebBrowser.Url.ToString)Why is it giving me this error?Its saying WebBrowser.Url is the problem.
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Sep 1, 2009
Im trying to create a login page which accesses a mysql database I keep getting this error: reference to a non shared member requires an object reference
[Code]...
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Dec 29, 2009
How do I fix the following error: Error 1: "Reference to a non-shared member requires an object reference."
On Line:
shortCut = CType(WshShell.CreateShortcut(creationDir & "" & shortcutName &
".lnk"), IWshRuntimeLibrary.IWshShortcut)
Here's my full code sample (if needed for context):
[Code]...
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Jan 25, 2010
I am getting the following error when I call another form from Form1 and fill out the text boxes and Press Ok button. For some reason I cannot access the datatable (dt) from Form1. It gives me the following error: Reference to a non-shared member requires an object reference
[Code]...
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