Why Isn't Invoke Via Delegate Built Into .NET
Sep 1, 2011
I understand that .NET is multi-threaded and that is a good thing, but I continually run into issues when I have a background worker for example that is updating some control on my form and I have to do:[code] My question is why is this not built into the framework - surely if I am trying to update a DataGridView it should be intelligent enough to know when the update is from another thread and it could do all the above itself?
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Mar 5, 2009
I'm trying to figure out if it is possible to instantiate and invoke a delegate by name, rather than explicitly. I think the code below explains it fairly well. I want to accept a function name and then instantiate the delegate based on that. In the example I use a select case, but I want to eliminate that and just use the methodName argument itself.
Private Delegate Sub myDelegate()
Private Sub myDelegate_Implementation1()
'Some code
End Sub
Private Sub myDelegate_Implementation2()
[Code] .....
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Oct 1, 2009
I'm working with the DevExpress XtraGrid control.I have a routine that goes thru and adds all the controls on the current form dynamically, and launches on a seperate thread the routine for a given control to initialize it to the value that will be displayed to the end-user. Some of the controls are displaying calculated values, and take some time to return their values, so that's why we are doing it on a seperate thread.
[Code]...
I'm using a similar snippet of code for any control properties that have to be updated, and all work fine. On the above code when the actual Invoke is called, it APPEARS that the thread just ends and never calls the delegate, and doesn't return to finish either.
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Aug 16, 2010
I have some code in c#
BeginInvoke(new MethodInvoker( delegate() {myAppMethod_Tick(sender, e); }));
Now, When I tried to convert that code to vb.net I have below..
BeginInvoke(New MethodInvoker(Function() Do myAppMethod_Tick(sender, e) End Function))
But it does not compile.. What's problem for it?
Because my c# application works ok without any problem..
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Feb 3, 2009
I have a few textbox for data display and RS232 communication in my application. After I send characters on RS232, I want text boxes display feedback characters from RS232 receive. So in SerialPort_DataReceived() i was told to use Invoke to display received characters on TextBox1, TexBox2.how to define delegate for TextBox1 and call Invoke()?
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Oct 12, 2010
I'm hacking away at some code which seems to have been started, at least in theory, as an MVVM project in Expression Blend, by my predecessor at this company.
I've got a thread running in the background, which is running some operations on items as they happen. In order to prevent any clashes, I've also got that thread running any operations my users call for.
Once those operations are completed, I'd like to bring up a MessageBox to give a summary of the user-initiated operations, but now that they're running off in their own thread, the finishedProcessing event handler is now running on the background thread instead of the interface thread and it's causing my MessageBoxes to appear non-modally.
Back in the WinForms days, I'd have handled that using InvokeRequired, Invoke and a Delegate. I've read that this has been replaced by something called "Dispatcher", but the ViewModel class I'm using doesn't seem to have a Dispatcher object.
The "thisViewModel" class I'm using inherits a class called "WorkspaceViewModel", which inherits "ViewModelBase", both of which look generated to me...
where I can link up to this "Dispatcher" from here?
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Oct 4, 2010
What is the Invoke syntax to marshall data from a background thread receive callback method to a function on the UI Thread?(Form1).
Public Class Form1
MyDelegate = New DisplayData(AddressOf DisplayData)
Private Sub Form1_Load()
MyDelegate = New DisplayData(AddressOf DisplayData)
[code]....
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Oct 25, 2009
I'm running into a strange error and I can't move forward Consider the following code
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Aug 4, 2010
D is a dictionary whose entry values are of Type T..What I'm attempting to do is have a delegate like "Serializer" below that I can invoke on an instance of T, such as "Entry.Value" below.Please see the "return Entry..." line below for my wishful thinking.[code]
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Jan 28, 2012
I'm having problems with a program where I've got some multi threaded activities addressing the states of check boxes, which in turn are created by a user definable interface To achieve this I'm using the code below, which works on some occasions and crashes on other occasions when it stops with the following error NullReferenceException was unhandled Object reference not set to an instance of an object.Delegate Sub CBSetCallback(ByVal cb As CheckBox, ByVal value As Boolean)
Private Sub SetCheckBox(ByVal cb As CheckBox, ByVal state As Boolean)
If cb.InvokeRequired Then
Dim d As New CBSetCallback(AddressOf CBset)
Invoke(d, New Object() {cb, state})
[code].....
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Mar 16, 2010
I've got the following code:
[code]...
The problem is that, when I call the "SetStatusBarText" sub from another thread, InvokeRequired is True (as it should be), but then my threads stall on the Me.Invoke statement - pausing execution shows them all just sitting there, not actually invoking anything.
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Jan 30, 2010
from the documentation we have this: Multicast Delegate: Represents a multicast delegate; that is, a delegate that can have more than one element in its invocation list.
so am i right to say that Multicast delegate is no different from a normal delegate other than the fact that it has arguments. so System.Action is a 'normal' delegate whereas System.Action(T)(Byval obj as T) is a multicast delegate?
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Feb 9, 2010
I've created a Delegate that I intend to call Async.
[Code]...
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Jun 1, 2010
Code:
Public Class SendPings
Shared Sub New()
AddHandler Post.Saved, AddressOf Post_Saved[code].....
I get a error" Method 'Private Shared Sub Ping(item As BlogEngine.Core.IPublishable, itemUrl As System.Uri)' does not have a signature compatible with delegate 'Delegate Sub WaitCallback(state As Object)'.
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Jun 29, 2010
Is it possible to immediately use code that is built in a dynamically built assembly?I would like to create an instance of an ENUM built using.http:[url]......
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Aug 27, 2010
I have a filesystewatcher object. On it`s event it runs a procedure which fills a treeview with a data. I had problems with treeview methods, but when I run them using invoke method everything is ok. But I still have one problem. When I load the form for the first time, everything works fine. But, when I then close the form (me.dispose, me.close), and load it once again, when Filesystemwathcer start the procedure i have an exception "invoke or begininvoke cannot be called on a control until the window handle has been created" trying to run a treeview.invoke method?
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Apr 10, 2009
What is Platform Invoke Service (P/Invoke)?
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Oct 13, 2010
We have a UI with a progressbar. I know how to invoke, safely, the control from which it was not created from a thread. there are threads being processed in a threadpool, all of which calls an "agent" (which is a notifier to raise an event back to the UI to then increase the progressbar). an "agent" is set as a property in a State object, which is then passed into a method which will be executed on the ThreadPool. so, I invoke on the UI the method to update the progressbar, but the bar does not seem to update at all (screen frozen) and it takes a very very long time for it to execute. without threading, no problem.
[Code]...
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Mar 23, 2010
I am trying to write a VB.NET alternative to a C# anonymous function.I wish to call Threading.SynchronizationContext.Current.Send which expects a delegate of type Threading.SendOrPostCallback to be passed to it. The background is here, but because I wish to both pass in a string to MessageBox.Show and also capture the DialogResult I need to define another delegate within. I am struggling with the VB.NET syntax, both from the traditional delegate style, and lambda functions.My go at the traditional syntax is below, but I have gut feeling it should be much simpler than this:
Private Sub CollectMesssageBoxResultFromUserAsDelegate(ByVal messageToShow As String, ByRef wasCanceled As Boolean)
wasCanceled = False
[code].....
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May 26, 2009
C# and VB.NET comes with built in types that maps to the CLR types. Examples are: int (C#) and Integer (VB) maps to System.Int32, long (C#) and Long (VB) maps to System.Int64. What are the best practices for deciding when to use built in types or not to use them (using the System.* structs/classes instead)?
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Apr 13, 2010
Is it possible to import a dll which is not built in .Net in a vb.net project like htis:Add Reference -> Browse -> CreatingDll.dll file
Or the <DllImport>attribute needs to be used in case where i want to add a .dll file which is not created in .Net within a vb.net project?
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Mar 28, 2012
I have a program that reads a .csv file which contains 378 lines with 16 fields. The problem is, I want this data to be built in to the .exe, instead of in a separate file. In the old days, it would have looked something like this[code]...
Is there an easy way to do this in VB, or am I going to be stuck writing 1 line for each 6064 actual variables? I know it is considered by many to be "bad" to have data built in, but this is what I am after.
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Sep 25, 2011
I need all the dll's in the following format:
Dim references() As String = {"Reference1.dll", "Reference2.dll"}
but I don't know where to find the dll names.
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Apr 22, 2009
While reading this threadthe code sample there came from MSDN, which was used to demonstrate the use of a delegate. I know what Delegates are. And I know how they work when it comes to things like crossing threads and even sinks.... how ever, the sample given is a simplecontrived example, and I'm wondering why/when would I use a delegate in this situation? Or in any situation? In my head, it seems it would have been easier/cleaner to call the function pointed to directly...
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Jul 30, 2010
It would be good if visual basic had standard math constants like pi, the Euler number, and others built-in so one doesn't have to define them each time and have the possibility of making typos. Even some of the physical constants in MKS unit could be included like the Boltzmann's Constant, speed of light, permittivity and such. Each could be a special simple like kb for the Boltzmann's constant. Or it could be a properties like phyconst.c for the speed of light, phyconst.kb for the Boltzmann's, phyconst.sb for the steffan-Boltzmann's constant, pmathconst.e for e=2.71.
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Apr 26, 2009
let's say my app is buit and i want to add xtra controls to the app.[code]...
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Jun 24, 2011
I want to code some thing up that logs you into a site and automatically posts to it.
I heard you need to use httpwebrequest but I've seen literally almost every tutorial on the subject and I am still super lost.
Also, is it possible to automate the built in web browser? I coded a semi-automatic program in the past but I want something automated.
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Nov 3, 2011
I have a problem where a button at the top left of a tab control will not appear in debug or compiled. There is no code telling it to hide.
Now, I can make it re-appear by moving it, then moving it back to the exact same position. If I then re-build it will be there.
It will then be there for a number of builds, at which point it might disappear again. This seems to happen for a few buttons in my project. The common factors are that they are on a tab control (standard dot net ctrl) and near the top left of a tab page.
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Mar 14, 2012
How is a bot for a game like Match 3 built? Match 3 type games are basically when you have different objects and you have to match 3 in a row either sideways or up and down.[code]
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May 14, 2010
i have an application that's in development, but some modules of the application are already built, so the application it's installed in several computers. In my code, i call an external class that i built with several functions that i use in multiple applications, in this class i have a small piece of code that checks in the network (internal), if a new version of the application (Msi File), of the current application it's available, and if it's available, it runs the Msi file.
msiexec /package MSIPackage.msi That worked fine in windows XP, but now some machines have been upgraded to windows 7, and the user need other credentials to run the package. (Elevate Privileges). Other problem it's that in my application i create several folders in the installation and the user doesn't get any permissions to write in the folders.For example i have one Log folder, and i can't write any logs to it.
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