.net - Boolean From Nothing Sometimes False - Sometimes Nullreference-Exception
Jan 26, 2011
coming from this question i was wondering why:
[Code]....
'this throws an "Object reference not set to an instance of an object"-Exception'
[Code]....
A CType(obj, Boolean) would evaluate to False(just as CBool(obj)), i think because the compiler uses a helper function, but that is not my theme. Why does casting Nothing to Boolean evaluates to False, whereas casting an object that is Nothing to Boolean throws an Nullreference-Exception? Does that make sense?
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Jun 29, 2011
[code].....
I m getting an error NullReference Exception was handled at this line of code
Dim snmp As New SimpleSnmp
snmp = New SimpleSnmp(host, community)
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Sep 26, 2009
I keep Getting a NullReferenceException Error but I have declared a NEW structure. See below:
Structure ISACReply
Public RTD As ArrayList
Public SAC As ArrayList
Public DRT As ArrayList
[code]....
When I try to execute the subroutine "calltest" I get a NullReferenceException in the line that says " rv.DRT.Add("HELLO") " even though I have set rv to an instance of ISACReply using NEW.
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Sep 23, 2011
I am developing a windows application in vb.net and getting an error of system.nullreference exception.I am trying to insert data in the database, insertion occurs in the first go. But, when i stop the porgram and re-run, i get the exception.
Imports System.Data
Imports System.Data.OleDb
Imports System.EventArgs
[code]....
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Mar 7, 2011
I'm getting a design time NullReferenceException on Dim db As Database = DatabaseFactory.CreateDatabase()and I can't figure out what to do about it. Has anyone experienced this problem or know the solution?
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Nov 19, 2010
I have a TreeView with a parent node and two children node. Each of the nodes contain a checkbox stored in a TreeViewItem. I want the two children node checkboxes to be set to IsChecked=true when the user checks the parent node and I want the two children node checkboxes to be IsChecked=false when the user unchecks the parent node.
[Code]...
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Jan 18, 2010
I'm pretty new to Vb so I'm not sure of all the correct terminology etc.
Private Sub Add_mousedown(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Add.MouseDown
Dim Addition As Boolean
[code].....
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Jan 17, 2011
This is probably a really basic (no pun intended) question, but I can't seem to find an answer anywhere.Why does the result of func1 return False and func2 returns True? On every other test I have done, integer 1 is converted to boolean true and 0 to false. Works ok if I just set rtnValue to 1 or 0.
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Aug 2, 2010
A week or so ago, you folks really taught me how to use the KeyData event. I adopted some of the coding to make my new code so much better. A few days ago, I thought I figured out how to run my little game. You see, you have two buttons. Comment and Uncomment. You Press Control + K and then after that, you press Control + (C or U) to activate the buttons. And I thought it worked! But my buddy figured out how to break it! The thing is, I need to figure out a way to make IsCtrlK (Look below) False if any key that isn't Control + C or U is pressed right after it. What would you suggest I look into using?
[Code]...
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Jul 28, 2011
I have a math program that I am working on. One of the exercises has a random word and 6 radiobuttons. The user has to select the radiobutton that displays the exact number of letters in the random word. What I am having trouble with is creating a Public Function to check if the answer selected is the correct one. The radio buttons are within a groupbox. The Public Function returns a boolean True or False.
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Sep 21, 2011
I have a HTTP class that gets content from URL's, POST's content to URL's etc and then returns the raw HTML content.In the function inside of the class it detects if there is a HTTP error and if so I would like to return false but will this work if I have declared the function to return a String?
Code Sample of what I am trying to do (Note the Return Content & Return False if a HTTP error code is detected)Public Function Get_URL(ByVal URL As String) As String
[Code]...
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Mar 8, 2011
i got this code from the net , but i can't make this code work on the system i am programming so, i used the same codes to another system and it worked, when i tried using it to my system, it failed, so i started a new program and it still fails... what is wrong with my program? here is a sample of the code:
[code]...
whenever i run the program, it compiles, but when i click the commit button, this message appears "NullReference Exception was unhandled Object reference not set to an instance of an objects" and it points to .NewRow
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Jan 5, 2010
I am getting this error when I try to print my report. Here is my print code.
Private Sub PrintToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles PrintToolStripMenuItem.Click
Dim Print_Dialog As New PrintDialog
[code].....
Here is my error: System.NullReference Exception: Object reference not set to an instance of an object.
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Feb 7, 2011
When the following executes, I get the error 'NullReference Exception' - Object reference not set to an instance of an object. TestClass has Get and Set methods for the integer property TestWord.How should the following be changed to let me set TestWord in six elements of TArr?
Dim TArr(5) As TestClass
For i As Integer = 0 To 5
TArr(i).TestWord = i * 10
Next
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Dec 16, 2009
It just return false no exception. Nothing.
Declare Function InternetGetCookieEx Lib "wininet.dll" Alias "InternetGetCookieExA" (ByVal pchURL As String, ByVal pchCookieName As String, ByVal pchCookieData As System.Text.StringBuilder, ByRef pcchCookieData As System.UInt32, ByRef dwFlags As System.UInt32, ByVal lpReserved As Integer) As Boolean
Public Function GetUriCookieContainer(Optional ByVal uri As String = "") As String
Dim result As Boolean
Dim cookiedatasb As System.Text.StringBuilder
[CODE].....................
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Nov 17, 2009
From what I read it is a good convention to name a method that returns a boolean value with the prefix of "is" or "has". So in keeping with this convention I am trying to name a method in my program with this prefix but I am running Specifically I have a class called Day. It is a simple class with a few data members and one method that returns a boolean value of true or false. The name of the boolean variable is isSpecialDay. This class has a method called isSpecialDay which takes the date of the day, applies some criteria to the date and then sets the variable isSpecialDay to true or false. My problem is that the boolean variable is named isSpecialDay and so it the method. What should I do?
Public Class Day
Private TheDate as String
Private DayName as String
[code].....
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Oct 27, 2011
After Filling a DataTable in GridView's DataSource . A column with check box Type appears but it created as read only column and I can't enable it or make it editable... even i tried .readonly = false and still can't be edited
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Sep 27, 2010
I have a function that gets a string passed to it.When testing the function, I'm getting a null reference exception on the string parameter that gets passed to it, even though the string is not null, I don't understand why I'm getting this error.I used a dummy value to verify both the string parameter in the SelectSingleNode function and the newValue string parameter being passed to my function and they both contain values, so I don't understand why it's throwing a null reference exception. Just for clarity, the purpose of the function is to write values back to the nodes of an XML file.[code]
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Mar 30, 2009
I have a function that gets a string passed to it. When testing the function, I'm getting a null reference exception on the string parameter that gets passed to it, even though the string is not null, I don't understand why I'm getting this error. I have a screen shot belowI used a dummy value to verify both the string parameter in the SelectSingleNode function and the newValue string parameter being passed to my function and they both contain values, so I don't understand why it's throwing a null reference exception. Just for clarity, the purpose of the function is to write values back to the nodes of an XML file.UPDATE
Private Sub setValue(ByVal nodeToMod As String, ByVal newValue As String)
''Test writing to xml config file
Dim dummy As String = "Config/" & nodeToMod
[code].....
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Oct 13, 2011
The second Case in the first Sub is the one giving the error message.The second Sub is the part I (Removing the Label so that it can be recreated later) fix this code block? I do not know the correct way of removing or desposing a Label, as you can see the Label
Public Class Form1
'<<< Indecating if the app. is in Reading, Editingor AddingNew.>>>
Dim ModeIndecator As String = "Reading"
[code].....
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Feb 20, 2012
I'm building a simple game in an ASP.NET/VB.NET web app. The game has a UI made up of several ImageButtons. The web page's code behind file holds an instance to the game object which will manage each turn taken by players. Everything worked when the Game object's methods were Shared. The problem occurred after refactoring to make the game object work as an instance instead of a shared class. Now, when the action returns to the code behind, the instance of the game object is nothing.
The code bits:
Public Class _Default
Inherits System.Web.UI.Page
Private _gamePanel As Panel
[code]....
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May 8, 2009
It is possible to catch an exception and throw a new exception which wraps the first exception as an inner exception: [URL] Also, if I call a function and it throws a certain error, but I catch it, will the calling code's catch handler execute? If so, and it is of a higher exception type, is this not wrapping the exception? eg I can throw exception ex of type IndexOutOfRange, log it but rethrow, catch a higher up exception and do something, or I can throw a new exception and wrap an inner exception like:
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Mar 5, 2010
I ran some code through an automatic translator for C# to VB, and it translated some code like this:Public Property Title As [String]How is this different to Public Property Title As String
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Jan 14, 2010
[Code]...
VS 2008 Null error "NullReference object was unhandled"
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Sep 2, 2009
I have a large project where we have 2-3 dll projects that are converted from VB6 to VB.NET. We have fixed all the issues that caused compilation errors, and most of obvious issues in running, so now we have basically a program up and running. The exe is created from scratch in VB.NET, using a lot of functionality from the converted dll's (including GUI forms). What I wonder is when I run the program in debug mode, I get a bunch of warnings in the "Immediate Window" saying:
A first chance exception of type 'System.Exception' occurred in Microsoft.VisualBasic.dll
...and some of other type (but most of them in Microsoft.VisualBasic.dll).I was wondering if this is common in projects converted from VB6, or if it is caused by bad design in our code...
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Jul 2, 2010
When I try to create a instance of a COM class it throws an exception as Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG))
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Sep 30, 2009
When I try to create a instance of a COM class it throws an exception as Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG))
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Apr 14, 2011
I'm trying to catch a user defined permission exception - i.e. a user does something their level of system access won't allow, permission exception is thrown. My problem is, the exception is caught and then rethrown as a genertic System.Exception.Is there any way I can deduce the original exception type, without resorting to string comparisons, like if ex.ToString.Contains("Permission denied"
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Jan 11, 2010
When catching an exception in .net, you can have as many type-specific exception blocks as needed. But I usually try to have at least one "general" exception catch block. But is there a way to get the type of the "real" exception thrown that is caught by the generic exception handler, perhaps using reflection?For example, if I have
Catch ex As System.ServiceModel.FaultException(Of InvalidUser)
ProcessModuleLoadException(Me, ex)
Catch ex As System.ServiceModel.FaultException(Of SQLExceptions)
[code].....
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Jun 19, 2012
i have about 20 possible exception messages that i want thrown when an error occurs.i need somthng like this when catching the exception
Try
' do domthing
Catch ex As CustomInvalidArgumentException
'do domthing
[code]....
do i have to create a class that inherits from Exception for each type of exception?
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