Automatically Recognize And Handle Changes Of An Item In A "System.Collections.ObjectModel.Collection"
Feb 4, 2011
I wanted to create a custom control with a custom Item-Collection in it.(Similar to the ListView Items, but with other properties)I wrote a Class that holds properties of a single Item data (ClassItemData) and another class that "Inherits System.Collections.ObjectModel.Collection(Of ClassItemData)". The Collection class contains a public event (ItemCollectionChanged) which is raised when "ClearItems", "InsertItem", "RemoveItem" or "SetItem" is called. (I used "Overrides" on all these functions and added the Raise Event to them.) The event is handled in the custom control itself and causes the control to refresh/repaint itself. The collection class contains also "Default Public Overloads ReadOnly Property Item(ByVal index As Int32) As ClassItemData" which returns the Item at the speciefic index.
The control refreshes itself when I place the control on a form and use code like: ControlName.Items.Add("TestItem") Unfortunately the control does not refresh itself when I use: ControlName.Items.Item(0).Visible = False The value of the Item itself has changed after this, but the control does know about the changes and does not refresh itself. If I do a manual repaint/refresh of the control, it looks all fine, but it does not work automatically. Does anyone know, what I have to add, so I can handle an event or something in the control when a property in the ItemData class has changed? How do I recognize changes in existing items and raise an event in the custom event?
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Dec 29, 2010
How can I have it so that you can add items to a System.Collections.Specialized.String Collection but only if it is not there already? I have already found the code, but deleted it and cannot remember it. It is something like[code]....
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Sep 21, 2011
I'm having a problem with this code in the highlighted line(*); getting the error in the heading.
Dim htmlarraylist As New List(Of iTextSharp.text.IElement)
htmlarraylist = *HTMLWorker.ParseToList(New StreamReader(tempFile), New StyleSheet())*
[Code].....
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May 20, 2011
If i wish to put items into a System.Collections.Generic.Dictionary, I can either Add or set the Item.I know if you do Add it helps you check if the key already exists and if not it throws an exception.Now I'm curious, so if I'm adding a ton of items, should I prefer setting Item instead of Add since Add does unnecessary checks that may actually slow things down?
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Feb 5, 2011
[code]...
What's really the point in using the former?It's hard to use linq if I used the former. I have to convert that to an array first which is difficult because there is no (asarray) function.I think I would change all of my code that's using System.
Collections.Specialized.StringCollection to System.Collections.Generic.List(Of String)
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May 20, 2011
in what situation will an item in System.Collections.Generic.List not be removed successfully?url...The way they phrase it makes me think that it is possible that a Remove operation on an item found in the List(Of T) could actually fail.
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Sep 16, 2009
Is there a way to create a collection of collections? e.g. I created a collection ListOf(Lines) After I add all my lines to it, I want to store this colleciton in another listOf(Collections). The reason I want to do this is because i want to create several separate collections of lines and I'll need to loop through them all to look for a certain line and I thought this would be a good approach if it's possible.
[Code]...
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Aug 11, 2011
I would use the System.Linq.Dynamic. I added the specified Dynamic.vb file, that starts like this:
[Code]...
to my (VB.NET)solution. Now Visual Studio does not recognize anymore in the project files the System.XXX references, proposing me to change them to Global.System.XXX
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Nov 24, 2011
I'm implementing a customized Graph algorithm in vb.net, and I'm having the following problem:
Supose the code:
dim col as new collection
dim myC as new system.collections.genericList(of myClass)
dim obj1 as new myClass
dim obj2 as new myClass
[code].....
'In the next statement, the myC2 inside col collection will be decreased to contain 'only obj1, like myC. I supose this is for myC and myC2 contains only a pointer to 'objects obj1 and obj2 as well col contains pointers to myC and myC2 myC.remove(obj2)'The problem is that I have to only copy myC to myC2, like a ByVal argument in a function,'instead a ByRef argument, in order to mantain a copy of objects in myC2 while these 'objects should be removed from myC. How should I do it?
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Jul 23, 2009
I have a Collection, the keys are strings and the values are Collections. In the sub Collections the keys are strings and values are Singles/Floats. How would I loop through all of the data? I need to get the keys and values not just the values. I've tried this but it produces a cast error:
[Code]...
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Oct 13, 2010
I am using Visual Studio 2005 and am writing a SSIS package. In the package I have a VB.Script that looks at a directory on a server and creates a list of the files. I then have a store Proc that looks at a table and gets a list of files that matches the files in the first array. The result is a fullresultset. The next step I need to create a 3rd array that only contains the rows from the first that are not in the second. However, I am getting the following error. Error: The script threw an exception: Unable to cast object of type 'System.Object' to type 'System.Collections.ArrayList'.
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Nov 5, 2010
I recently discovered that the standard System.Boolean value is actually 32 bits - this seems pretty "far out there" since it's only ever going to be 1 or 0 - I found this information in somebody's blog which contained 3rd-party documentation on the System.Collections.BitArray. According to this blog, the individual Boolean is 32 bits while the individual index entry in a BitArray is actually just 1 bit - official documentation here at
MSDN indicates that in reality, the BitArray is just an array of Boolean Values (which would be the same size as any other boolean) that provides methods and functions useful in deconstructing System.Byte values into the BitArray and reconstructing the BitArray back into a System.Byte (same with System.Byte()).
I'd rather not go through a lot of code to restructure Boolean Arrays into BitArrays unless there's going to be some genuine memory-use improvement (which I'd expect to see if I converted large Boolean arrays - at 32 bits per index - into large BitArrays at 1 bit per index). I'm also interested to know if the Boolean is actually a 32 bit monstrosity.
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Jan 29, 2012
I need to create a program, and now I want some advice from you, as I simply don't have so much experience to get round it.Firstly, I have issue with a checked list box. For example, there will be 5 items.I want each item to have a different value, because it will be a things people will be buying, and so when someone clicks on item1, the value I assigned to it will be output into a label, so user will know how much that item costs. I know how to output it, label1.text = CheckedList Box1.SelectedIndex but how do I set for example for item1 value of 5000, for item2 3500 and etc? Secondly, I will have a page for users, where they will see history of their bought items. But what's the best way to store the price they paid, item they bought and date? It should be able display for each user their own bought item history.I hope you understand what I meant, as I'm quite new in programming so It was a bit hard for me to express what exactly I want. If you didn't understand something, or need more information please ask me. I hope someone will be able to help me, as I really have a bit of a struggle with it. At first I wanted to use plain .txt file to store and output into textboxes, but it wouldn't be aligned, look nice and etc. Then I thought about database, but how to recognize which item to display for each user and etc.
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Jul 29, 2011
I am getting following error whenever I want to use IIf function inside entity framework query.
LINQ to Entities does not recognize the method 'System.Object IIf(Boolean, System.Object, System.Object)' method, and this method cannot be translated into a store expression.
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May 14, 2012
I'm getting an error after sending a list to a web service.This is the code that is calling the web service:
Dim sProgramInterest As New List(Of Integer)
crmService.InsertProspectGetId(sProgramInterest.ToList)
But I'm getting this error.
[code].....
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Mar 28, 2011
I can't seem to get it to recognize System.Data.OracleClient. I downloaded and installed the 11gR2, added a reference to Oracle.DataAccess. Looks like there is a 4.112.1.2 and a 2.112.1.2 versions. I'm tried adding both to the project, but neither are giving me access to that assembly. i.e.
[Code]...
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Jun 20, 2012
I recently implemented a solution to take an SSIS package and reconfigure the connection strings of the package using VB.net.[code]...
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Mar 21, 2012
I had a code segment on an asp.net page in the code-behind file. I decided to move it into a public subroutine in a module (general_functions.vb). Once I did this, however, the code no longer works - it throws an error. On the original code-behind I replaced the original code with a call like so:
[Code]...
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Oct 19, 2010
I am trying to change the image in a picture box using a combobox with item collections 0-8.When I run the program no matter what I choose in the combobox it selects case 0 and willnot change. code below for selected index changed.
Private
Sub ComboBox1_SelectedIndexChanged(ByVal
sender As System.Object,
ByVal e
[code]....
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Oct 6, 2010
I am trying to solve an issue in my application where the following exception is occurring: there is already an open datareader associated with this command which must be closed first. I am using TableAdapters, which maintain their own DataReaders, and everything seems to work fine unless I am interacting with one of my background workers.
In my code, I shadow the Item property of my collections so that I can retrieve the actual data from the database if needed. Here is a sample:
[code]...
Now each reference to the Item get property instantiates its own DataAdapter, so I am confused as to how the same DataReader will ever be used in this scenario. Is there something I am missing? All the TableAdapters do in fact use the same connection object, but I wouldn't think that would be a problem
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Feb 7, 2011
i need to automatically click upload button and input the values automatically in a website using web browser control
i know how to do this
For Each element As HtmlElement In WebBrowser1.Document.GetElementsByTagName("button")
If element.OuterText.Contains("upload") Then
[Code]....
does sendkeys.send "filename.flv" works fine or any other method works fine
input automatically the file name on the open save dialog box and click open button
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Nov 19, 2009
I am having trouble developing an asp.net page. I can create custom collections and use them in win apps, but when i reference the system.collections namespace, the page response hangs up. No exception info is passed back or anything. The page just freezes. Is this a common problem. I am wondering if its due to the assembly not being present (but am unsure why an exception wouldn't indicate this.).
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Jan 27, 2010
imagine i want to add an extension method to System.Collections.Generic.List(Of T)
let's say i want to give it .GetUBound which returns Count-1
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May 17, 2012
ok this code will save data withc is URL from textbox and load it to listbox , but i want it save first name of uRl like google then in other textbox put URl and save so when its load data its shows only name like Google not [URL] in listbox sometimes the link is too long and it will be not good interface in form1 and then when u click Google in listbox it open its URl [URL]
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
My.Settings.FavList.Add(url_text.Text)
[Code]....
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Feb 2, 2012
I have a lists of different custom classes and each must be sorted severals times before the algorithm is complete. For each sort I wrote a comparer. Sofar so good. Everything works. But: By now I have abou a dozen different comparers in more than one class and it is still getting more. I wonder if there is a way to limit the number by writing a new general function that can be used to sort all lists without the need for a specific comparer.Below is what I've got so far. But it does not work.
"System.Collections.Generic.List(Of ClassA)" can not be converted into "System.Collections.Generic.List(Of Object)."
[code].....
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Oct 29, 2009
Public extreme_foods As New System.Collections.ArrayList()
[Code]...
anyone know why extreme_foods(i)=s is giving INDEX OUT OF RANGE??
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Jun 1, 2011
I have a fairly lengthly block of code that I'm trying to convert from VB6 to VB.NET. The ArcObjects GIS code basically looks at a table and groups a bunch of GIS layers together and adds them to the ArcMap table of contents. I'm having trouble with this line when testing it in Visual Studio 2010: [Code]
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Jun 10, 2012
I am trying to pass a System.Collections.Generic.List to another class. The collection is created in class2 and then passed into class1
[code]...
However I get a 'Null Reference Exception error' when I run the program. It seems f_str in the line 'For Each s As String In f_str' is null.
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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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Jan 10, 2012
Firstly, i have a grdData at my main page. After choosing the data i want and went to another page using
[Code]...
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