Updating Observable Colelction From List?
Oct 7, 2009
I have my datgrid's itemsource binded to a observablecollection. Every 5 secs my client app resceives a list from the server which i use to update the observable collection. The problem is that when it updates the grid seems to reset (if details is open when i update the details collapses, if i have an item selected it will un-select)
Here is the code that i am using to update my observable collection:
Private Sub creategriddata()
Dim svc As New ServiceReference1.Clientthing then re-adding
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May 6, 2012
I am using a Dim All_PriceLists As System.Collections.ObjectModel.ObservableCollection(Of BSPLib.PriceLists.PriceListPrime) where PriceListPrime implements Inotify for all properties in it.
I bound the All_PriceList to a datagrid as DataGrid1.ItemsSource = All_PriceLists but when I do All_PriceLists=Getall() where Getall reads and gets the data from the DB, the datagrid is not updating.[code
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Nov 26, 2008
I use a List(Of T) (where each T is a custom type with a few members) to keep track of about 500 items that change all the time. The list can be changed from different locations within the program (uses background workers that monitor the list).
Question: Is there some built-in way to prevent the List from being updated from different locations or from different threads at the same time? For example, one thread may remove an item from the list while another location changes one of the members of an item, causing conflict, wrong data and errors. Perhaps there is a standard way in VB.Net (framework) to solve this type of problem?
I use VB2008 (VS2008 Pro) and WinXP SP2.
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Oct 3, 2011
I am creating some user controls in vb using winforms. I ran across the observable collection and INotifyChanged events and was wondering if this type of action was available in winforms As I understand it, the observable collection is a WPFapplication, but it would be nice to use this type of functionality in a winform as well.
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Jan 30, 2012
I'm still teaching myself how to bind and use observable collection. One problem that I'm a little confused on is binding multiple classes/observable collection to one page. In other words, if I have a PersonName class and a AnimalName class, I have to create two separate observalbe collections for each? How would I set the datacontext when a page only allows one?
[code]...
Now If I add another class, how would I combine the two on the binding part and collection part.
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Mar 13, 2012
I've been working on this problem for a while and I'm clearly missing something...I create, populate and bind an observable collection like so:
Dim _ObservableWEI As New ObservableWEI
...
_ObservableWEI.Add(New WEI() With {.WEInum = 1, .WEIvalue = 1})[code].....
The problem is the filter effects the contents of both listboxes. I guess I need a specific instance of the collection to apply the filter too or something
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Feb 1, 2012
I will be doing an MVVM Project soon and I'm working a couple tutorial/examples out. How do I take the following code and connect it to a database. If I were to have a datagrid, how can I change information in the datagrid and have it automatically update? I'll be using MS SQL.
[Code]...
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Jul 7, 2009
I am trying to create a list box that can have things added and removed from it with the use of add and delete buttons in subroutines, i have also got a limit of 20 as the maximum number of items in the list box, also i would like the list box to be able to update the number of items in it after the user adds or deletes items from it: here is my code:
Public Class Form1
Private Sub cmdAddZp_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdAddZp.Click
[Code]....
the first part is for limiting the number the user can add to the list box, the second part is the delete function and the last part is trying to count the number of items in the list.
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Jun 18, 2012
I have a list box like this,
<asp:ListBox ID="ListBox1" runat="server" Height="175px" Width="213px">
<asp:ListItem Value="all">All</asp:ListItem>
<asp:ListItem Value="programmer">Computer Programmer</asp:ListItem>
[code]....
and a Grid View like this,
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
DataSourceID="XmlDataSource1">
<Columns>
[code]....
Grid View is getting values from a XML & XSLT file. What I want to do is, when user selects suppose Computer Programmer from list box, the grid view should get updated with the results of only those have this program. How can I do this? Do I have to bind the xml with List Box?
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Feb 21, 2010
I have an ItemsControl in a ScrollViewer. The ItemsControl.ItemSource is set to the Observable Collection.Every time I add an item to the collection, my application nearly doubles in memory usage and eventually after enough adds.
Here is a rough sketch:
<Scrollviewer Name="MyScroll">
[code]....
Using ANTS Memory Profiler, I can see all the class instances in my App. When I start the program, I have 150 instances of TextBox (There are three in the datatemplate). When I add a studyunit to the collection, I have 303. Adding another leaves me with 456... 609... etc.The studyunit objects inherits from dependency objects and I am only binding to its dependency properties. I made the studyunit a series of dependency properties due to this article: [URL], but it didn't fix anything.Update 2/22/2010. Here is the actual code (code above was very simplified and created from memory)
Private Sub ObservableCollectionChanged(ByVal sender As Object, ByVal e As System.Collections.Specialized.NotifyCollectionChangedEventArgs)
If e.Action = NotifyCollectionChangedAction.Remove Then 'q removed
[code]....
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Sep 28, 2011
How to sort items in ListView by column bound to an Observable Collection ?I've looked all over the place and I can't find anything easy enough or simple on this.
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Apr 12, 2010
So I have a list of names in a .txt file. Where is a place I can type in all the names I want and press save and get a link so they can see the list. Then I can remove a name and press save and the name will be gone. And or add a name. So basically I need a website where I can type something and keep it uptodate. I've tried ripway but after you edit the list and save it it doesn't change.
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Sep 1, 2009
I have a Public Sub I am using to enumerate running processes and then display them in a ListView.I want to be able to update the list automatically each second. I've thought of doing this in two different ways, but the method that I want to use is checking if the process has exited or not.
When reading up on the Process Properties, I ran into .HasExited and .Refresh.I thought that I could use a timer and have it tick at 1 second intervals. I would then check, each second, if the Process has exited. If it has, remove it from the list.The problem with this, is that I don't want to put the sub in the timer because it would just constantly flicker the control. I need to figure out a way to access the variables inside of the Sub while inside of the Timer's .Tick event.The other issue is being able to add processes that aren't there. Which I can within another sub. I was thinking I could create a sub that grabbed the Processes by ID, compare them to the list, and them add them if they aren't there. If I did this, I could also remove Processes by ID that aren't in the list.
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Nov 1, 2011
What I am trying to do is to instantly apply a filter to a large list of data such that the list is updated almost immediately regardless of the number of items in the list. I have this working using a listview right now but it is far from instant, a list of 5000 items takes over a minute to get through. What I do currently is to maintain a cache of my data that my listview entries are based on. When the user selects a filter I parse this data one item at a time and determine if each item should still be displayed in the listview, if not I remove it. The complexity of determining whether or not a data entry meets the filter requirements is O(1), but just getting through each element in a loop takes significant time, and so does updating the list view graphically at the end of the process.
I have considered using a datagridview instead, using a database connection. I have never done this before and my main question here is whether this would allow me to do what I have described. With the database I could form an SQL query to return only the items that meet the new filter requirements... but would the data in the form update immediately, or would there still be significant delay?
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Mar 23, 2009
what i'm working on is, i have VB with a loaded Access DB, and i'm using a query to display the information, in a list box and in indivual labels. i have it so it will allow new entries to be made, however i can't figure out the exact code to get it to update to the program the only code i currently am able to show is this since everything is basically being done through access
[Code]...
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Dec 10, 2011
I am currently trying to develop an application which will backup large folders to a specified destination. To find all the files in the specified 'backup' directory I am using the following code.
[Code]...
I have tried putting my GetFilesRecursive function into a separate background worker to run first so I can update the GUI however I am struggling on how to return the List of found files back to my application (I get cross-threading exception) and how to update the progress bar to show the progress of the GetFileRecursive function so the user knows it is processing the list of files and has not crashed/frozen.
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Aug 20, 2011
I have a WPF ObservableCollection which is bound to a ListBox and I have a Sort() method which when called will convert the ObservableCollection to a List(Of T), and undertakes a sort based on a date/time column within the collection.
The data is sorted, even when new items are added to the ObservableCollection, however the date/time isn't being correctly sorted. The data is sorting based on the date however it is very much random when it comes to the time portion. The following is an example of the outcomes I am experiencing:
[Code]...
Is there anything that I am doing incorrectly in this method that would cause the time portion not be included in the sort? Is there a better way of doing a sort?
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Jan 25, 2012
I have a webpage with a form that is used to edit some object. This object contains a Collection of other objects defined like this: Public Overridable Property Employees As List(Of Employee)
On a form I can delete an employee, add a new one or modify existing one. When I click save new values are sent to the server. On a server I check if the user exists. If exists then I modify its values, if it does not exist then I add it. All employees that exist on the server and were not sent are marked as deleted (State changed to EntityState.Deleted). I try to use the following code (dbCollection = database entities, newCollection = collection sent from the form):
[Code]...
This code does not work, because changing to EntityState.Deleted removes the object from collection, and for each loop breaks, since the collection is modified...I know that I can overcome this problem by using a for loop or adding objects to delete to some other list first, but I hope maybe there is a pattern that would make my code nicer.
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May 14, 2009
II am trying to create a toggle button that switches a list to a range and then back to a list if needed. I am able to get it to do both but when I add an item to the list, convert to a range and then convert back to a list it leaves off the last items I entered.I tried to work in a code to select all cells but I must not be putting it in the right place.This is what I have so far:
ActiveSheet.ListObjects.Add(xlSrcRange, Range("$A$3:$AE$7"), , xlYes).Name = _
"List1"
I realize the problem is the $AE$7 (the $A$3 is correct)
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Oct 27, 2009
In VS 2008, VB.Net, I am successful connecting to a local SQL Server (version 8) and seeing all tables/views/procedures in Server Explorer. The local OS is Win XP Pro SP3. I created an ODBC data source to a remote SQL server (also version 8) with a database of the same structure as the local one. The connection tests out ok. The remote computer runs Windows Server 2000 SP4. In the VS 2008 Server Explorer I add this ODBC source. When I click on the plus-signs to expand items, neither the tables nor the views show anything, whereas the full list of procedures appears. Is it the old SQL Server version? Is it the old Server OS version? Something else alltogether?
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Dec 30, 2010
This is what I'm sure will be the first of many noob-ish questions from yours truly... I'm studying as a mature student for a Computing Degree (encompassing web design, hardware, programming and systems analysis). The programming seems to be my weak spot this year. I enjoyed C++ last year, doing basic console applications, but progamming visually with VB in Visual Studio 2008 I'm struggling!
[Code].....
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Oct 16, 2009
Does link text mean I have to return a concrete implementation? Even though I am using svcutil with the /r that includes my entites(where IMyInterface is defined). I get no errors but it changes all List(of IMyInterface) to list(of Object) and I cannot deserialize it on the client
Error: list(of object) cannot be converted to list(of IMyInterface).
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Oct 1, 2009
I'm looping all the properties in an object via reflection:
For Each p As PropertyInfo In values.[GetType]().GetProperties()
If p.CanRead Then
'Do stuff
End If
Next
how to determine whether the property in question is a generic List(Of T)? If it is I need to loop the list itself.
I've experimented with GetType and TypeOf but have not managed to get anything working.
To clarify, I want to keep this generic. I do not want to specify the type of T, I need to loop the list items and call the ToString method on each item. T could be one of a number of different types (application specific reference types). Is it possible to do this without specifying types?
(VB.NET 2005 with .Net 2.0)
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Nov 18, 2009
If I can generate a list of random integer with a click of the button and put the results in a list box using VB.Net but how do I randomly change several integer number generated by button 1 by clicking button 2? How I retain the results of button1 and change the results when clicking button2?I try before but the two button function code cannot relate to one another.
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Mar 23, 2011
Public Class notifierMain
Public Class Contacts
Inherits List(Of row)
Public Sub New()
[code]....
When I debug this winforms application I get curType = "notifier.notifierMain+Contacts+row" I want to the Validate function to know it is in MyContacts. How do I do this?
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Oct 27, 2009
In VS 2008, VB.Net, I am successful connecting to a local SQL Server and seeing all tables/views/procedures.I created an ODBC data source to a remote SQL server with a database of the same structure as the local one.The connection tests out ok. In the VS 2008 Server Explorer I add this source. When I click on the plus-signs to expand items, neither the tables nor the views show anything, whereas the full list of procedures appears.How can I see the lists of tables and views in Server Explorer for an ODBC source?
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Nov 5, 2011
I wish to make a project where a teacher views a list box with a list of students of a class. When he selects a name from the first list box the second listbox would change its data to show the grades for that one student.
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Apr 12, 2010
I have implemented inheritance for two parent classes called Table and Field. Each parent class has several child classes. In the Table parent class, I created a method that expects parameter List(Of Field).
I get an error when trying to pass in parameter List(Of ChildField) to the method that expects a parameter of List(Of Field). The error message is as below:
Value of type
'System.Collections.Generic.List(Of
com.hlb.icisbatch.data.ChildField)'
[Code]....
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Mar 16, 2011
This program is supposed to allow the user to check items in a checked list box. If the item is checked, it goes into the Completed List Box on the right. The program then adds the unchecked items to the Pending list box on the left. I keep getting placement values (e.g. O,1,2) instead of the strings (e.g. "Key Returned") in the list box results (see photo attached)
Public Class frmCheckOut
Dim i As Integer
Dim cleaning As String = "Cleaning Inspection"
Dim damage As String = "Damage Repaired"
[code].....
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May 16, 2011
Another program I am working on for fun, I am basically shuffling a list inside a listbox, what I want to do is delete the rest but not sure how to go through with that. At the moment I have this: [code] Just contains the code, declarations outside weren't included.So anyway, once clicked, it will call on the function to basically shuffle in a for loop, I was wondering if I should (or how should) create another function and call it in the click button or have just a loop in the click button so it deletes half the list. What I am doing is I have 20 list of items, I want the program to shuffle the items and then deleting the lower 10, meaning, if I had 10 items and wanted 5 top, I'd want: 0, 1, 2, 3, 4 and deleting 5, 6, 7, 8, 9.
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