Binding And Threads In WinForms?
Oct 27, 2010
In my Winforms application, i've got a form and an associated business layer class. All controls are bound. When i click a button i call a method on the class which then starts a background worker and returns. The background worker does some processing and finishes.
The problem i'm having is that i'm using a label to display any error messages generated by this background worker, which is fine but after a set time i want to clear the label, so for that i'm using a timer (on the business layer class), which, when it fires, is on a different thread and thus should not update the property that the label is bound to Whats the best way to do update the label? -- Should i be using a delegate to update the property value, if so how do i invoke it?Note i'm also having a problem with getting the databinding of the visible property on this label to work.
View 5 Replies
ADVERTISEMENT
Jan 4, 2011
In a .NET 3.5 Winforms app, after a user provides a username and password, I set a custom principal in the CurrentPrincipal property like this:My.User.CurrentPrincipal = Service.GetPrincipal(username)This is done in a method that is called using Invoke, because the originating thread is not the UI thread:Invoke(New Action(AddressOf doLogin))But when I click on a button in the Winforms application, the CurrentPrincipal property has been reverted to its default, the current Windows user.Dim lPrincipal = My.User.CurrentPrincipal ' not my custom principalApparently, using Invoke while setting the principal does not solve the problem. Is there another way to set the CurrentPrincipal property for all threads in the application?
View 1 Replies
Sep 23, 2010
I have this code
Public Sub FillCategoryCombobox(ByVal categoryList As List(Of tblCategory), ByVal LvName As ComboBox)
LvName.Items.Clear()
Dim itemValue = New Dictionary(Of Integer, String)()
For Each category As tblCategory In categoryList
itemValue.Add(category.CategoryID, category.CategoryName)
Next category
LvName.DataSource = New BindingSource(itemValue, Nothing)
LvName.DisplayMember = "Value"
LvName.ValueMember = "Key"
End Sub
I receive an error on
LvName.DataSource = New BindingSource(itemValue, Nothing)
Value cannot be null
View 3 Replies
May 4, 2011
What is the best way to bind a property to a control so that when the property value is changed, the control's bound property changes with it.So if I have a property "FirstName" which I want to bind to a textbox "txtFirstName" text value. If I change FirstName to "Stack" the txtFirstName.Text also changes to "Stack".
View 1 Replies
Aug 24, 2011
You have a pseudo-table class and a pseudo-row class. The row is somewhat generic and has no strongly-typed fields. It follows the typical dictionary interface
Dim age As Object = person("Age") 'accessed via default property Item
vs
Dim age As Integer = person.Age 'an actual property typed as an Integer
What's the pattern to use so that we can bind our pseudo table and its rows to a grid or combo box?
Dim rs As New clsResultSet(tblPeople)
Dim id As Object = rs(0)("Id") '913
Dim name As Object = rs(0)("Name") 'Ted[code].....
View 1 Replies
Jul 8, 2009
Am in the process of architecting a new windows forms application, and I intend to use Visual Basic 2008 and SQL Server Express 2005. This is my first application in .Net and I really want to observe the best OOD & OOP principles to create an application that is easy to maintain and extend (add new functionality). My issue is in regard to databinding on the UI. From experience, what do you guys recommend to use for databinding? Should I return datasets/datatables from my Business Layer and bind these to UI controls or should I return Business Objects and bind these to UI controls? And what are the pros and cons of each approach?
View 1 Replies
Oct 19, 2011
I just had a new, last-minute idea on to take on a task, so I am running to StackExchange for quick help.
What I want to do is execute a series of methods right in a row, each in their own threads. I want the application to wait until all of these threads are completed, after which the program will resume. It also has to use managed threading (thread pool).
What quick examples could you provide to help me along the way? If it's too complex, what things should I know about so that I can Google it on my own?
View 1 Replies
Dec 30, 2009
I have a main thread which is designed to be a batch processor - it spawns a series of 'child' threads from a loop (which can vary in terms of the no of items) - see below
[Code]...
However, each of the 'child' threads could take anywhere from milliseconds to about a minute to process - depending on the complexity of each calculation. There may also be a large number of child threads - e.g 100s. Creating large numbers of child threads is not efficient. I therefore want some way to effectively queue each child thread (and cancel if the process is taking too long to complete). Autoevents seems like one way of doing this, but the only examples I can find seem to assume there are two different processes on seperate threads, not one process being repeated.
View 4 Replies
Nov 15, 2009
I'm looking for a line or two of code that will bind a DataSet.Datatable column to a textbox on a Datarepeater?
View 2 Replies
Oct 29, 2011
is there any way that i could link/bind multiple binding source to only one binding source navigator?
View 4 Replies
Oct 18, 2010
binding navigators, datagrid view, binding source are all sql database parts.Will these parts still work if you havent got sql on you pc and your not using an database file (.log and .mfd) and your not coding to them, im using MS Jet/Oledb to code to Excel.What not to put on an Employee evaluation: This employee has hit rock bottom and shows signs of starting to dig.
View 2 Replies
Jul 2, 2011
Binding Master Table to TextBox and DateTimePicker and Binding Details Tables to Datagridview then Add / Update / Delete in both
View 8 Replies
May 28, 2010
Is it possible to set a project default for VB.NET winforms projects so that the default Modifier for controls added to winforms is Private (not Friend)?I know there's a "modifiers" property in the properties window so I can set it for each individual control however I would like to change the project so from now on myself and other developers have to specifically decide to change from friend to private. (Which I would strongly discourage them from doing).I believe there is no way of doing this, but on another forum a while ago someone mentioned it would be possible with an add-in (but didn't name the add-in or where to get it).
View 1 Replies
May 29, 2010
I use objectbinding to display client data in a datagridview. The datagridview also contains a counry-column allowing the user to choose the country of the client.Unfortunately, databinding of comboboxcolumn does not seem to work if an own business class is used. Using a simple collection instead works well.Copy the sample code into a new windows project and the programm runs fine. Then comment and uncomment the two lines with "XXX" and the code will fail. Why and does anybody know how to make the sample code work by using the business object class(variable named "newClientListVariable" in the sample)? [code]
View 3 Replies
Aug 19, 2009
I started programming in VBA, then graduated to VB6, and I am now using VB.NET 2008 Express.I have read, in the various posts, that I should keep Option Explicit and Option Strict both on, in order that I use correct VB.NET code and not VB6.I am trying to do that but am totally confused with the results of one of my programmes that was running perfectly with Option Strict off, but now advises:Option Strict On disallows late binding. To me it appears that I am using early binding, but to be honest I am not clear on the binding situation. I have checked through a number of google items, and a number of this Forum's items without seeing the light.[code]
View 8 Replies
Sep 5, 2011
i have this code:Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
[Code]...
Error 1: Option Strict On disallows late binding.Im using visual basic 2010 express on a gateway laptop thats running Windows 7 OS How do i resolve this error?
View 2 Replies
Apr 9, 2009
I have a listbox and it it I am showing numbers.It should look like this (line by line) 1,2,3,4,5,6,7,8,9,10,11.....but is is showing it like this 1,10,11,...2,20,21...3,30...ow can I make it that it will show it in number order 1,2,3,4,5......
View 5 Replies
Sep 14, 2011
I need to run TWO Threads in a web application, .NET. 3.5 Both methods MakeRedCars and MakeBlueCars need to run at the same time as both take 5 seconds. I have tried many example codes with very bad results. I dont need anymore than 2 threads. The main issue I am having is knowing how to wait till they are finished and also how to store the results from each.Each of the Methods do different things, one is a web request, one is a sql call.
Both methods return a list of(cars) for example do:
carList.addrange(MakeRedCars())
carList.addrange(MakeBlueCars())
for each car in carlist<br>
response.write(car.colour + "<r>")
next
I have implemented the answered below and with empty objects all works well, as soon as you hook in a database call that returns the data/objects studio does a JIT and crashes.
View 5 Replies
Jan 28, 2011
I can only run "so many" threads concurretnly, a notion which I have seen elsewhere.As a threading novoice, how can I determine the maximum number of threads to use? Or is this a "how long is a piece of string" question? What does it depends on? Hardware config or what?
View 4 Replies
Apr 18, 2010
it would be best if I just copy and pasted the code (it's very trivial).
Private Sub Main() Handles MyBase.Shown
timer.Interval = 10
timer.Enabled = True
End Sub
[code]....
An exception, "The object is currently in use elsewhere", is raised during the tick event.
View 1 Replies
Oct 25, 2010
I am having an issue where I need to implement a type of thread scheduling... I'm looking to implement a list of tasks, each with a set time that they need to execute, and after the time is up they will execute the respective code that goes with that task. I would use a timer based solution, however, I don't think that it would be very efficient. There will be a very large list of tasks, some of which need to be executed within seconds of being placed in the list.
View 1 Replies
Jun 10, 2010
I have 2 thread.One that put some data inside a list?the second that take out these data from the same list.what is the best "list" that allows one thread to put something inside and another one that take stuff out>
View 1 Replies
Nov 7, 2010
My application generates some background threads to perform some slow jobs (a cycle of ask for a long process to a server - wait - download the result).
View 5 Replies
Feb 25, 2009
I'm having a bit of an issue killing threads off and resetting my form. After starting the threads, everything runs fine. When I want to cancel the threads, the threads are all killed off "properly" using the Abortable Thread Pool, but how do I know that all the threads are dead? I've tried using both GetAvailableThreads and GetMinThreads compared against the thread count that should be running if they're all killed off, but I can't seem to get it to work. The only time I can get the GetAvailableThreads to return the "correct" number is if I freeze one thread and kill off the rest.
View 7 Replies
May 28, 2010
I have a GUI that is running for a form, let's call it Class xWindow. It has finished processing data and is simply waiting for the user to press a button, i.e. the main thread has nothing to do. Just before it finished processing, it kicked started something that has a callback function which occurs in a new thread (e.g. a system timer or a Bonjour callback to say that a service has been found on a port). This callback occurs within the xWindow class.
[Code]....
View 10 Replies
Dec 22, 2010
Suppose I have created 70 "rule-finder" objects, and I want to run each one on data.This is a time-consuming process.The new computers with the I7 chip can run 7 processes in parallel, and so I was thinking of running 7 threads at a time. Asone thread ends, I would add another, until all 70 objects are used. When the last rule-finder has completed, I would resume the main course of the program.
View 5 Replies
Jun 1, 2009
how can I let two threads communicate with each other by using VB.net?
View 3 Replies
Jan 25, 2010
I currently have a program that runs several "intense" queries. I added a textbox and presented status updates when a query was starting, eding and how many were left. This would suite my need, but the textbox doesn't actually display anything until all the queries are finished. It then displays all the updates at once. I'm assuming updating the textbox in another thread would solve this issue, and that is where I am lost. How can I use a thread that receives a message from the main form running the query and have it display it in the textbox?
View 4 Replies
Feb 25, 2009
I'm making a Tabbed Web Browser, and I need favorites to add to this web browser, I was searching this forum for answers on how to do it and I ran into some threads tlaking about XML and how they are easily controlled, yet a little more complex. How do I do this? Where do I start?
View 2 Replies
Jan 23, 2011
Take a look at the code below. Here I create a thread, set its name, and start it:
Private Sub fileCreated(sender As Object, e As FileSystemEventArgs)
Dim processFileThread As Thread = New Thread(AddressOf fileCreatedHelper)
processFileThread.Name = e.FullPath
processFileThread.Start()
End Sub
This is the sub that is the thread: Private Sub fileCreatedHelper()
[Code]...
View 2 Replies
