Why Use A Delegate
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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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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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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Feb 11, 2010
I heard once that .net introduced an already defined delegate with no parameter that we could use instead of creating one.
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Nov 23, 2009
I came across a snippet of C# code which is very useful. I am trying to convert it to VB.NET, but can't seem to.
timer.Tick += delegate { panel.Children.Add(source); timer.Stop(); };
Is it possible to translate this to something similar in VB?
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Jun 28, 2010
I have below code in C#:
[Code]...
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Aug 3, 2011
I'm having trouble converting a C# delegate to VB.NET.
How can this be done?
public MainForm()
{
InitializeComponent();
_twain = new Twain(new WinFormsWindowMessageHook(this));
_twain.TransferImage += delegate(Object sender, TransferImageEventArgs args)
[Code]...
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Oct 28, 2011
how can I convert the following code from C# to VB without exposing "variable" as global variable.
[Code]...
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Dec 31, 2009
I'm in the process of converting some existing code to VB. However, I'm running into a bit of a snag. It seems that in C#, a delegate can have a return value, but not so in VB. So my question is, how would I convert the following VB code to handle this?.[code]
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Jun 20, 2009
im developing a way of calculationg differentil equations in VB 2008 using the 4th order ruge-kutta method. I pursched a book by Jack Xu called "Practical WPF Graphics programming".
[Code]...
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Jan 1, 2010
how this is written in VB.NET? This was an example I found on [URL]
ThreadPool.QueueUserWorkItem(delegate
{
var channelFactory = new ChannelFactory<ISimpleService>("*");
var simpleService = channelFactory.CreateChannel();
var asyncResult = simpleService.BeginGetGreeting("Daniel", null, null);
[code]....
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Jul 8, 2011
I am using this delegate to invoke my methode:
[Code]...
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Apr 5, 2009
for few solutions it work outs well but not for the following code. I find an error when executing the following code. I find an error :
ErrorMethod 'Public Sub test()' does not have the same signature as delegate 'Delegate Sub DataRowChangeEventHandler(sender As Object, e As System.Data.DataRowChangeEventArgs)'.C:UsersKashifDocumentsVisual Studio
[code].....
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Dec 23, 2008
I have a problem in translating a piece of C# code
(
http://www.codeproject.com/KB/WPF/VMCommanding.aspx)static bool ConfigureDelayedProcessing(DependencyObject depObj, ICommandSink sink) { bool isDelayed = false;
[code]....
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Apr 7, 2009
I am trying to create a delegate(as a test) for: Public Overridable ReadOnly Property PropertyName()As String My intuitive attempt was declaring the delegate like this:
[code]...
So the question is, how do I make a delegate for a property?
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Jul 30, 2010
This is a theoretical question, I've already got a solution to my problem that took me down a different path, but I think the question is still potentially interesting.Can I pass object properties as delegates in the same way I can with methods? For instance:
Let's say I've got a data reader loaded up with data, and each field's value needs to be passed into properties of differing types having been checked for DBNull. If attempting to get a single field, I might write something like:
if(!rdr["field1"].Equals(DBNull.Value)) myClass.Property1 = rdr["field1"];
But if I've got say 100 fields, that becomes unwieldy very quickly. There's a couple of ways that a call to do this might look nice:
myClass.Property = GetDefaultOrValue<string>(rdr["field1"]); //Which incidentally is the route I took
Which might also look nice as an extension method:
myClass.Property = rdr["field1"].GetDefaultOrValue<string>();
Or:
SetPropertyFromDbValue<string>(myClass.Property1, rdr["field1"]); //Which is the one that I'm interested in on this theoretical level
In the second instance, the property would need to be passed as a delegate in order to set it.
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Dec 22, 2009
Try5Times will try a function for 5 times.that function can have any number of argument and return a boolean.
If the function return false, try again.
If the function return true, stop.
How to make such function and delegate? Is there a general delegate?
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Oct 2, 2011
Here there's an old question about this code.
xmpp.OnLogin += delegate(object o)
{
xmpp.Send(
[code]....
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Jun 8, 2012
I'm trying to convert the c # code of a sample code to vb.net but I could with the following line of code. it is an event, delegate. but I can not build a functional structure.
[Code]....
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Mar 19, 2012
I have a code from Fleck that actually works fine in the C# (no errors)and this is a line in a class library:[code]can someone tell me what is the valid vb .net code for that?
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Aug 26, 2011
I've got interface:
[Code]...
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Apr 20, 2010
I'm having an issue with an application suite I'm developing. The bulk of the work is done in a backend dll that relies heavily on delegate subs in the different apps.
The problem I'm having is, I have a lot of these delegates typed to require a parameter. (eg, Public Delegate Sub DelTypeA(ByRef param As Object)). The individual methods will have a DelTypeA as one of their params, and I will pass it AddressOf functionA that has that signature.
This works fine for strong typing as long as the signature is something incorrect (2 params, a byval instead of a byref). But if functionA has NO params, the delegate is still created!
This works fine if I genuinely don't need to use a param, eg if the sub is simpler and I would have ignored the param anyway. But I want the strong typing to work here.
EDIT: I should add that invoking the delegate also works fine for simpler subs; the param is just not passed because it had nowhere to go. But I want to force all the subs to match the signature and do their own ignoring of the param
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Mar 27, 2012
I've been fooling around with this for two hours and getting nowhere. I want to update a list box on a form with some text. Unfortunately the event that calls for the update is a timer which gives me a cross thread error.The listbox relies on a combo box which tells it the number of items to display. Here's my sub that performs the update.
Public Sub EventUpdate(ByVal EventMsg As String)
Dim DateTimeStamp As String = Format(DateAndTime.Now, "MM/dd hh:mm:ss")
With lbxEvents
[code].....
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Feb 2, 2011
I have one master page and then content page on the master page and also have one UC on the master page, now i want to filter data from usercontrol on and populate on content page using delegate.
I have achieved this in C# but i am not able to do this in VB.NET
Because in VB.NET i am not able to overload event of the uc.
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Dec 14, 2010
I am struggling to retrieve custom attributes from a method. As you can see, the method ProcessXML has a custom attribute. The method itself gets passed into an anonymous delegate and then, in that context, I'm looking to get its custom attributes, but I'm not sure quite how to do it.
Here's my code
Public Sub UpdateXML()
Dim errors = New Errors
Dim xml = <testxml>
[code]....
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Mar 13, 2012
I'm trying to update a DataGridView via a Delegate. This is part of a simple application but the initial query takes 4-5 seconds to generate. I want to FillSchema to build the DataGridView so the application launches quickly and then updates the data.[code]...
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Jul 24, 2009
Is it possible to make a Delegate to a Constructor? For example:
Class Bar
...
End Class[code]......
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Oct 6, 2010
In my application, I have a MainWindow with a ToolStripProgressBar and a ToolStripStatusLabel.
This properties:
Property ProgressBarPercantage() As Integer Implements BCSXPSearchTool.Presenter.IMainView.ProgressPercentage
Get
Return Me._progressbarpercentage
[Code] .....
The code above is working. But if I change the sub runproc() to:
Public Sub runproc()
Dim statusToSub As delegateStatusTo = AddressOf statusTo
Dim percToSub As delegatePercTo = AddressOf percTo
' statusToSub.Invoke("Test")
percToSub.Invoke(50)
End Sub
It doesn't work. I get an exception:
InvalidOperationException
I got the text something like:
The access to the control, created by another thread from another thread is not allowed.
I'm using Visual Studio 2008 Express + VB 2.0.
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