VS 2008 Adding Items To A Collection?
Jun 25, 2011
I am trying to add the file information of the contents of a folder to a collection. Although I am getting the collection to hold the correct number of items that the folder contains, all of the collection's items are the details of the last file in the folder.
I'm trying to use a loop to go through each item contained in the folder and then adding the item details to a collection with the following line
nCounter += 1
collFileDetails.Add(NameOfItem, nCounter)
Next NameOfItem
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Apr 6, 2012
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]......
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Mar 17, 2009
i have created my own custom propertythe property is of type collection ,it displays a form which allow the user to add a list of images and strings,it stores the data in a collection ,my problem is , i have noticed that after adding items to the collection at design time , there is no code generated in the .Designer file of the form and there for when i close the for / save it and reload it , all the items that i added to my custom property are gone.my question , what did i miss here ? how do i make my custom property generate code at the .designer file for the items i have added to my property?
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Apr 11, 2010
I know you are going to lough about this , but I guess I deserve it ...I am sure I am doing something wrong , but I can't find it out ...I have created a collection , lets sayMyCollectionI have also created a class , lets call itMyClass
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Apr 15, 2010
CAUTION: Noob using Win32 API ahead
I want to display a list of open windows on my computer in a rich text box. So, I'm trying to store the names of all windows in myString, and then set RichTextBox1.Text = myString.
Here's the code
Imports System
Imports System.Collections.Generic
Imports System.Collections.ObjectModel
[Code].....
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Jan 16, 2010
I'm trying to create an inherited version of the ListView control that (among other things) should have a different background image if the listview is empty to if it has items.Obviously you can easily enough test the count of the collection, but I need to be able to react to the event, however there doesn't appear to be any event related to adding/removing items.
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Feb 13, 2010
I have two tables "Person" and "Alias" in a one to many relationship. I have a DGV for "Person" and want to use a combobox for the Aliases. I also have a textbox and a button for the user to type the alias name and click the button to add the alias name to the combobox and update the dataset. I keep getting the "Items collection cannot be modified when the DataSource property is set." Error. But if i use a DGV instead of a combobox for aliases, I have no errors and everything works fine. If I remove the datasource property for the combobox it will not get populated with the data already entered, so how, or can I, set it up where the combobox gets populated when the form loads and able to add items to the combobox????
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Jan 12, 2009
I'm working on building my own UserControl that will display thumbnails. I've got the collection and the items that the collection holds working ok, and I've got a handle on how I'm going to display the information on the face of the UserControl. However, my problem is how to fire the Method that displays the thumbnail on the face of the UserControl when a new Item is added to the Collection?
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Jul 30, 2009
I have a class that contains a collection of another class. See below
Public Class Spot
Private mActive As Boolean
Public Sub New()
[Code]....
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Jan 6, 2010
I want to retrieve the selected items in a listbox, save them to a collection, and then use that collection later. I thought that was simple enough, but when I clear the selected items in the listbox, my collections (items, indices) change. I found this out by stepping through the code.
Basically what I'm wanting to do is move items in the listbox up or down (up in this case), and still keep them selected.
[Code]...
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Oct 28, 2009
I am trying to extend the functionality of the ToolStripPanel control (which is a panel hosting ToolStrips that can be moved during design-time, as I'm sure you know).One thing I wanted to add was a 'ToolStrips' property, which would be a collection of ToolStrips the user can edit via the collection editor in the designer. So instead of manually placing ToolStrips on the ToolStripPanel via the toolbox, the user can just use the property to add/remove (or even edit) them. This is of course similar to how you add/remove/edit TabPages in a TabControl.So, I came up with this code, which I have used successfully in the past for other controls:
Public Class cToolStripPanel
Inherits ToolStripPanel
Private _ToolStrips As New ToolStripCollection(Me)[CODE]....
The cToolStripPanel control inherits the ToolStripPanel control and adds the ToolStrips property, which is of type ToolStripCollection. That class, in turn, inherits the Collection(Of ToolStrip). In the InsertItem method, I add the 'item' ToolStrip to the cToolStripPanel. Of course I also need to override the RemoveItem / ClearItems methods but that's for another time.I am 100% sure that this code should works, at least for other controls. If you replace ToolStrip with Button (for example), I can add buttons via the property during design-time just fine, exactly the way I want it.But it seems that ToolStrips are special. When I try to Add a toolstrip (via the collection editor Add button), a null reference exception occurs. I've been trying to debug this all day and I've finally come up with a possible candidate for the problem... (I've actually used design-time debugging for the first time ever, which was pretty cool, and which showed me that the InsertItem method is not run!)
I think the problem is that the collection editor cannot create a new instance of the ToolStrip class. I can remember when trying to inherit from the ToolStrip, I was forced to add a constructor, because the ToolStrip "has more than one constructor that can be called with no arguments".Perhaps this is causing my problem? Do I (and if yes, how?) have to somehow control the creation of a new instance of the ToolStrip? Or am I completely off track and that is not what is causing the problem? I'm sure that it's a problem with the ToolStrip class, since I can use the exact same method with other controls just fine. It's only when I change the type to ToolStrip that it starts getting angry at me....
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May 3, 2009
I have a listvew that is setup like:
[COLUMNHEADER1] [COLUMNHEADER2] [COLUMNHEADER3]
[CHECKBOX] Graham
[CHECKBOX] Greg
[CHECKBOX] David
What i was trying to do is put text in [COLUMNHEADER3] besides each of the names, so if "Graham's" details exist then put "PASSED" beside the name "Graham" and "FAILED" if it's failed, i'm not sure how to access the 3rd columns details to put that in is it:
formname.listview1.subitems("")
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Aug 11, 2010
I am currently working on some tools and I am having some troubles adding new lines in a listbox.
vb.net
For i = 0 To lstFiles.Items.Count - 1
Process.Start("C:UT2004Systemucc.exe", "compress " & lstFiles.Items.Item(i))
If IO.File.Exists(lstFiles.Items.Item(i) & ".uz2") Then
[Code].....
The meaning of this code is that if the file exists, it will add a new line called Success below the dragged fileline. If the file doesn't exist it will create a new line called Fail below the dragged fileline.
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Mar 12, 2010
How would i add all registry (subkey, parent, etc) items to a treeview?
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Aug 31, 2009
Ive added items to my menu strip, cut , copy , paste etc. but i dont know how to code them im using a tabbed web browser incase that makes a difference
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Nov 16, 2009
I am very new to Visual Basic, and I need to add items from my database to the ListView control. I have a table in the database called tblChannels that I would like to draw the information from and populate the ListView control in VB, in the form of a column. I currently am unsure about how to go about doing this. Previously I have created combo boxes that draw the information from the database, but trying this method for the ListView does not work how I want it to.
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Feb 3, 2010
I have some code which addes values into the items and subitems, which works fine.
vb.net
Case "Aa en Hunze"
Dim Lvi00 As New ListViewItem(New String() {"naam", "blabla"})
Dim Lvi01 As New ListViewItem(New String() {"adres", "blabla"})
Dim Lvi02 As New ListViewItem(New String() {"postc/plaats", "blabla"})
[Code]...
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Apr 13, 2011
Aren't arrays of object enumerable?Look for the comments in the code
Public Class AddressCollection
Inherits System.Collections.ObjectModel.Collection(Of AddressType)
Public Sub New()
End Sub
[Code]...
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Apr 11, 2012
I have a simple subroutine that loads a list from a database. I would like to be able to use the same code to load a ListBox and a ComboBox by defining the list type as the common abstract base class ListControl, and see no reason why I can't - except that VB.NET doesn't expose/implement/whatever the Items collection in ListControl. I note with frustration that this is not the case in ASP.NET. At moment my code is ugly because I have to check what type of list control I have passed in, in order to cast it to a type that has an Items collection. (My code may be ugly for numerous other reasons too, but it is beautiful to me). Is there a way to rewrite the code to avoid having to go through the testing and casting nonsense? (I've stripped it down somewhat so that all that remains is where the problem lies).
Sub loadList(ByVal db As SqlDatabase, ByVal strCommandText As String, lstHost As ListControl, Optional bClearList As Boolean = True, Optional bIsListBox As Boolean = True)
If bClearList Then
[code]....
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Mar 1, 2010
i am trying to sort the items in a collection(of T), by the start date. but i do not know how to do it. i do know that we have to implement list properties.
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Dec 2, 2011
I have a class that represents some business object, such as this:
Public Class MyObject
Inherits SomeBaseObject ' Implements INotifyPropertyChanged and IDataErrorInfo
Private mMyVariable as Integer
Public Property MyVariable as Integer
[code]....
SomeBaseObject implements both INotifyPropertyChanged and IDataErrorInfo, such that a Validate method will populate the appropriate IDataErrorInfo fields when setting the property values.I also have a collection that supports change events, which I eventually bind to a WPF DataGrid.
Public Class MyCollection
Inherits ObservableCollection(Of MyObject)
End Class
Part 1: Let's say that I have a business rule which says that no two items in my collection may have the same value for MyVariable. How do I set up my events (or implement additional interfaces somewhere) to perform this cross-item validation whenever the property value changes on any item in the collection?
Part 2: Suppose I have a list of integers such that whenever I add a new MyObject item to an instance of MyCollection or change the MyVariable property on any item already in the collection, the value of the MyVariable property must exist in this list of integers?
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Apr 18, 2011
I often have a class defined and I also define another class that is simply a collection of the other class. To do this I found it easiest just to define the other class as Inherits List(Of Type). The reason I define a collection class is to add extra functionality to the collection. Take the following code for example.
Class Car
Property Name As String
Property Year As Short
[Code]....
how can I define my own collection so that I can reference it by index or name like that. Right now I can only reference it by index.
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Oct 20, 2009
removal of items in a collection or list using the " For Each " statement to iterate through.This code works:
For Each item As ListViewItem In ListView1.SelectedItems
ListView1.Items.Remove(item)
Next
This code does not:
For Each itemChecked As Object In CheckedListBox1.CheckedItems
CheckedListBox1.Items.Remove(itemChecked)
Next
I have been reading on this for hours today to find out why the first code block works, but the second does not.What I've learned is the "For Each" statement implements the IEnumerable interface. I have seen these terms used many times and scratched my head when it didn't make scense, then just moved along, something to strain my brain about later.Today was later...So since the IEnumerable interface is used, the .GetEnumerator method of the IEnumerable interface is called upon at the beginning of the "For Each" block, this evaluates the collection or list as in: For Each item As ListViewItem In myCollection This is done at the beginning of the iteration through the myCollection, so if the myCollection is altered as in:
For Each itemChecked As Object In myCollection
CheckedListBox1.Items.Remove(itemChecked)
Next
The altering of the list returns the error:List that this enumerator is bound to has been modified. An enumerator can only be used if the list does not change.
[code].....
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Jun 15, 2012
I am trying to work out a way to group a collection of items like an enum so that I can access them through code else where in my program. i.e I have list of items and sub items
[Code]...
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Jun 15, 2012
I am trying to work out a way to group a collection of items like an enum so that I can access them through code else where in my program.
i.e I have list of items and sub items
CODE:
I would then like to be able to access then like: G1Level1.Leve2.Leve3
Would anyone be able to advise if this is possible or achievable.
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Mar 12, 2010
I am creating an instance of a Generic List collection and I am surprised to find that I can't add more than one value to it at a time. I was thinking there was going to be something like what you can do with arrays, where you can add a group of values to it at creation. I saw the AddRange method, but that seems to add another collection to the end of this collection, which is not what I want. So my code is:
vb
Dim MyList as New List(Of String)
MyList.Add("John")
MyList.Add("Bob")
[Code].....
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Sep 27, 2011
I'm trying to populate class properties where one property is a list collection. I get a NullReferenceException when trying to add to the list collection. The code (litlle bit simplified) is here:
Public Class Portfolio
Property Name As String
Property Assets As List(Of Asset)
Public Sub Populate(ByVal data As DataTable)
For Each row As DataRow In data.Rows
[Code] .....
I have a nested class "Asset" inside the class "Portfolio". Everything goes ok until the line
Me.Assets.Add(asset)
Which gives me the NullReferenceException error.
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Jul 12, 2011
I've done a little bit of LINQ but I almost exclusively return some elements from a collection based on some criteria. Now I'm trying to do something similar; let's say I have 50 winForm Controls in a collection - I want to set the .Visible property = True based on the controls name.
How would I do that? Below is my failed attempt.
myControls.AsEnumerable.Select( Function (myControl as Control) ( myControl.Visible = (myControl.Name <> "Hidden")) )
It compiles and even executes but does nothing.
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Nov 10, 2009
I have a ComboBox control with some items added to the items collection in design mode. What I want is when an item is picked from the ComboBox a different value is actually used in the code, instead of what is displayed. I am aware of the DisplayMember & ValueMember properties, but I'm not sure if that is what I need to use. All the examples I found were for bound data.
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Jun 16, 2009
I have a problem getting the collection of items in the ItemMouseHover event. I want to get the collection of all the items and subitems when the Mouse Hovers in the ListView. I have the property of Full Row select in the ListView.
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