Possible To Instantiate And Invoke Delegate By Name?
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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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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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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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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Dec 13, 2011
If I have a console application containing the class
[Code]...
I'm not a VB.NET guy. Am I correct in assuming I need to instantiate my object first? Why does the VB.NET example differ?
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Sep 28, 2009
I have created a WebSite with a folder called Classes. In the folder, there is a class with a Public Shared Function. How do I go about instantiating that class so I can use that function on a web form?
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Jun 11, 2009
I'm trying to decide whether to get a value, call it X, in my class through a read only property or through a function. Normally I'd code it as a property except in this case the GET involves doing a lookup to a sql table. So there's way more overhead than a simple RETURN X. So my question is, when I instantiate a new object from my class, are all the properties calculated at that point, so that the sql lookup will occur too? Or is the property only evaluated when I actually reference it in the calling code.
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Jun 5, 2009
I want to instantiate and name a listbox based on the value of a textbox. If the listbox already exists by this name (textbox value) I want to add items to the list.
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Jan 7, 2010
I sort of understand why this is happening, but not entirely. I have a base class with a Shared (Static) variable, declared like so:
Public Shared myVar As New MyObject(arg1, arg2)
In a method of a derived class, I set a local variable like so:
Dim myLocalVar As MyObject = myVar
Now when I do something like myLocalVar.Property1 += value, the value in Property1 persists to the next call of that method! I suppose I get why it would be happening; myVar is being set by reference instead of by value, but I've never encountered anything like this before. Is there any way (other than my workaround which is to just create a new object using the property values of myVar) to create myLocalVar by value?
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Oct 31, 2009
i wanted to do something simple that sort of replicate an object:
public function clone(byval realcopy as object) as object return new Control ' something like this works, however i want to return the type of realcopy, which may not be a control end function so i tried this:
public function clone(byval realcopy as object) as object
return new gettype(realcopy.gettype)
end function
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Jan 24, 2011
Just a bit of an issue that we're trying to resolve here. Assuming We're implementing a business model as one dll and a data access layer as another dll. We want them to be de-coupled so we implement an interface for the data-access layer. Great, we could now swap out the data access layer and, as long as the new data access layer fulfils the interface we're good to go, right?
Except we're not. In the business model we need to insanciate the data access layer and, because you can't instanciate an interface, you have to instanciate the actual class. We need to know the name space and the class name.We're going to end up with a line of code somewhere in our business model that looks something like this:-
Dim test as iDataLayer
test = new namespace.DataLayer
Basically, we can declare test as an iDataLayer (the interface) but to instanciate it we need to refer to the actual class (DataLayer). So we haven't really removed the coupling. If we want to swap out the data layer for a different implementation with a possibly different class name or namespace then we need to ammend the code in the business model. We're trying to avoid that.
So far the best we can come up with is to use the activate instance method instead of the New keyword (Late Binding). Because that takes a string we could hold the namespace and classname in a config file or similar, so swapping out one component wouldn't invalidate the others, you'd just need to update the config. That's just our home-spun solution though and I can't help feeling there are betters ways out there.
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Jun 5, 2009
I have defined an interface named IEmployee (ID, FirstName and Surname properties) but I have not yet implemented that interface in any class. What I want to do is something like:
Dim User as New IEmployee
User.ID = 1
User.FirstName = ""
User.Surname = ""
Call SomeFunction (User)
The VB.NET complier does not seem to like this.
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Aug 25, 2011
what actually goes on inside the pc when I reference an object vs when I instantiate it.
Like this
Guys joe; (reference)
Joe = new Guys; (instantiate).So what goes on inside the computer for each line above.
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Oct 13, 2011
this is what i want to do. I have a class library project into my solution. Into it i have a class. I want that class to be instantiated as soon as the solution starts. So it can be accesible from the other projects in the solution like this: Namespace.InstanceOfTheForm.Property Is there any way to do that? or something close to that?
[Code]...
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May 5, 2010
I used different backgroundworkers to instantiate some 'heavy' forms thinking that it will reduce the time to instantiate them if I did them at once but it looks like I am wrong since it is still taking about 43 seconds to load all of them. Am I missing something or do you have a tip on how I can speed up their instantiation?
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Feb 17, 2012
Presuming "instantiate" is the appropriate terminology, may I get some insight as to which of these are better, more efficient,[code]...
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