.net - Collection Initialisation Using Iif() Throws ArgumentNullException?
Jan 31, 2012
why this gives an error at run-time:
Dim mightBeNothing As List(Of String) = Nothing
Dim a As List(Of String) = IIf(mightBeNothing Is Nothing, New List(Of String)(), New List(Of String)(mightBeNothing))
I am getting ArgumentNullException on the second line. If I replace the last part with:
Dim a As List(Of String) = IIf(mightBeNothing Is Nothing, New List(Of String)(), New List(Of String)())
It works - but the constructor New List(Of String)(mightBeNothing) will never be called if mightBeNothing is nothing, so what is the issue?
I've been having problems with following code on some computers, while it's worked super on others (most):
Dim xmlSer As New System.Xml.Serialization.XmlSerializer(GetType(XMLContext)) which produces the stacktrace: System.ArgumentNullException: Value cannot be null. Parameter name: type at System.Xml.Serialization.XmlSerializer..ctor(Type type, String defaultNamespace)
How can that code throw that exception, when the argument is drawn from a gettype call, and note that it doesn't happen when debugging on my own PC, only when it's installed on some of the client PC's???
I have a question that regarding the initialisation and setup at the daily startup of a winform app.The startup requires a httprequest to login to a remote website, to obtain a cookie container for later processing. It uses the Keep Alive method to stay open as long as the sub is open.
My question is (perhaps naiive?) how can I keep the cookie container, and any other variables stored in memory kept there so they stay in scope while I the application is doing other things throughout the day?
For example, I have a sub in a class that takes care of the login to the web site and stores the cookies, once the sub ends, the cookie jar empties out. I could keep loging in again but that seems like extra processing to call the process instead of jsut keeping it in memory. I guess I could write the cookies out to a table and read back in, but perhaps there is simpler way?
all classes inherit docMain and addTemplateToList( X ) adds x to a List(Of docMain). Now my question is: Is there a better way to do what's done in the code sample? I thought of something like:
I have written an MDI text Editor and I have written a "save" sub routine, please see below
'This sub routine updates the current document or calls the save as routine Private Sub SaveToolStripButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SaveToolStripButton.Click, SaveToolStripMenuItem.Click
[code]....
I am testing this sub routine today and it throws up an error during runtime when a new document is created and the user (me in this case) writes a few lines of text, I click the save toolstrip button and because its a new document, the save as sub routine is supposed to be be invoked, however the application stops running and I get this error message "ArgumentNullException was Unhandled" from Visual Basic.
[code] I'm basically trying to see if a record already exists. My problem is when I run this I get a "ArgumentNullException was unhandled" error It occurs on the line "dbAdapter.Fill(output)" in the sub.
I am using 2005 and I am getting a ArgumentNullException when I try and debug my program. I have included the error and a piece of the code. I am not sure how to fix this error at all. If more of the code is needed I can post it.
Public Class MainForm Dim sPIServer As String 'PI Server Connection Storage Variable Dim myServer As PISDK.Server 'Variable to hold the server to work on[code].....
i have an ASP.NET page which has a numebr of user controls within it. There are 2 user controls which are of interest. I need to display either one of them or neither of them, depending on the record selected previously.
In the user controls I need to set properties of some controls which are in a FormView. So in my user control code-behind I have a number of properties which look something like this:
I'm getting the following exception when I try to run up my Winforms app and haven't been able to find a solution to it:
System.ArgumentNullException was unhandled Message=Value cannot be null. Parameter name: activationContext
[code]....
I've added a handler for the "unhandled error" event in the applicationevents class but it never reaches that stage and there is no source code running that I can break into and diagnose.
The application was fine until I added a user control (nothing fancy, just a standard windows user control) and then dragged it onto a form in the app (user control and form were in the same application). The application builds and compiles without any errors or warnings but when I attempt to run it up I get the above error straight away.
Does anyone have any idea what it could be or even how I can go about investigating it? I'm a bit stumped on this one as I'm not sure how to investigate it. I removed the user control from the form and then I removed the user control from the application entirely but the error hasn't gone away. In all honesty the addition of the user control might be a red herring but the problem manifested straight after adding it.
Is it good practice to store sub-collections of item X inside a parent collection of item X for caching 'filter-queries' which are performed on the parent collection? (They won't be used together (as in color AND type).) Or is it also ok to just Loop over the collection and return the correct entities in a temporary collection?
I have been researching for a couple of days now and to no avail. Does Anyone know how to make a custom collection that take advantage of the collection editor? I would like to be able to have 3 Color Values, 1 Boolean and 1 String.
I'm trying to support Basic.NET on my framework so I'm trying to convert C# 4 code to Basic.NET 10. Microsoft is committed to "co-evolve" these two but I'm having a problem with collection initialization... I found that I can initialize a collection much like in C#:
I've got the following ADO.NET Entity Framework Entity Data Model:I want to find all the Policyholders with both a Service of a given Id and also a Keyword of a given Status.
This LINQ Does Not Work:
Dim ServicesId As Integer = ... Dim KeywordStatus As Integer = ... Dim FoundPolicyholders = From p As Policyholder In db.PolicyholderSet.Include("Keywords").Include("Services") _ Where p.Services.Id = ServicesId _ And p.Keywords.Status = KeywordStatus _ Select p
The Where clause cannot search the p.Services and p.Keywords EntityCollections in that way.
currently in my application I have a Global Collection that is a Collection of Collections.Currently I am trying to add items/ elements to one of the child collections of the Global Collection but I am unable to use the collections methods of the child.When I assign a variable to the child collection and return the collection it is just an object with the collection inside.
Ex: Dim GlobalCollection as New Collection Dim ChildCollection1 as New Collection Dim tempCurrentCollection[code]......
I've been working with a CMS called InsiteCreations 2008. I'm running into an error I just can't wrap my head around. I would even be willing to compensate anyone a small amount over paypal, for a solution. The error is rare in occurance, and appears when clicking about 3-4% of links to other pages within our CMS.The full code page is quite large, but there seems to be only one function associated with the error. The error also only appears when not logged into the CMS. If logged into the CMS, clicking the link simply displays the page as normal. I have already checked permissions on the page from the CMS admin console, and it is public.
The error message is as follows:
Server Error in '/' Application.Collection index must be in the range 1 to the size of the collection. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Public Class Store Public Overridable Property Areas As List(Of Area) End Class Public Class Area
[code]....
What's the quickest way to get a total count of shelves for a store? I.e. for a store I get the total count of areas by using Areas.Count Or will I need to loop through each area and tally the count of shelves?
I have an ASP.NET app with lots of textboxes all over the page that need updating at various points through program execution. These textboxes actually belong to a certain class, so for easy updating I thought I could create a Dictionary(Of string, object) and add the control.ID and the control to it and then for updating do something like this:
I need to convert a VB Collection to a modern one, like Dictionary or Hashtable. For my approach, I need the Collection's KEYS. Googling tells me that it's impossible. Re-writing the entire application using new collections is not an option as the application is really old and large (converted from VB6 to VB.Net).Using the old Collection also is not good - as there are new components in development.Converting a - for example - Hashtable to Collection works:
using VBCollection = Microsoft.VisualBasic.Collection; public static VBCollection ToVBCollection(this Hashtable table) {
I use DataGridView in my project. Everything worked fine until I added some code in the RowValidating event. During the form_load event exception is thrown on the statement that set the datasource of the DataGridView.The project uses bindingsource for the datasource of the DataGridView. My validating code is shown below:
Dim currentRow As DataGridViewRow = Me.dgExpenditure.Rows(e.RowIndex) Dim incexpCell As DataGridViewCell = currentRow.Cells(0) If Not Me.closingBoolean Then
I debated whether or not to ask in the database section, but decided this was probably more of a VB question, than DB.I'm performing a query on my database and add its value to a DGV. At the moment, I'm just running tests to make sure the base example works so I can expand on it for more advanced tests.[code]It doesn't matter how I add the row, just adding it causes the error. And yes, the AllowUsersToAddRows property of the DGV is set to True, which wouldn't cause this problem anyway, but I decided to be extra careful.
I am using a dataset to pull data from a DB. One of the fields in a row is NULL. I know this. However, the following vb.net code throws a StrongTypingException (in the autogenerated get_SomeField() method in the dataset designer):
If Not IsDBNull(aRow.SomeField) Then 'do something End If
According to documentation and this question it should be fine.
i want to run a query and use the result for something else in my vb.net code. I have, opened the connection, passed the query and the connection object to the SqlCommand object and read it with the datareader object. The DataReader's HasRows property's value evaluates to true but i get an InvalidOperationException when i want to access the results of the query with the DataReader.[code]
I'm currently building an application in C#, using a basic design I came up with in VB.net for applications involving openGL. Using the Tao framework in VB, I have the following method:
Private Sub checkForGlutInit() If glut_initialized = False Then Glut.glutInit()
I'm having an issue with updating a couple list boxes in the form load procedure. I have an array created from a MySQL database, and when I try to add that array to more than one ListBox, I get: A first chance exception of type 'System.ArgumentNullException' occurred in System.Windows.Forms.dll
I have a program that throws out a string of six numbers from 1 to 37, what I need to do is check the the string for for a format you could say.I need to make sure the set of six numbers doesn't contain 4 or more numbers of the same numbers from the same set of ten(s).
Like this:I can't have: 1-3-6-7-8-12 Or 12-14-16-18-20-21 Or 21-23-26-28-30-31 Or 30-32-34-36-20-22
I can have : 1-3-6-12-17-23 ////////////: 12-14-16-20-21-22 ////////////: 20-1-13-23-26-30 ////////////: 1-37-22-33-30-9
I'm getting a "IndexOutOfRangeExeption was unhandled" in my project
Private Sub LookUpButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LookUpButton.Click 'Look up the information on the state.
[Code].....
I'm about ready to give up and go another route. I just thought I'd ask here.
