Custom Event - Invocation List Implementation Considerations
Apr 9, 2010
I'm looking for some pointers on implementing Custom Events in VB.NET (Visual Studio 2008, .NET 3.5). I know that "regular" (non-custom) Events are actually Delegates, so I was thinking of using Delegates when implementing a Custom Event. On the other hand, Andrew Troelsen's "Pro VB 2008 and the .NET 3.5 Platform" book uses Collection types in all his Custom Events examples, and Microsoft's sample codes match that line of thought. So my question is: what considerations should I have when choosing one design over the other? What are the pros and cons for each design? Which of these resembles the inner-implementation of "regular" events?
Below is a sample code demonstrating the two designs.
Public Class SomeClass
Private _SomeEventListeners As EventHandler
Public Custom Event SomeEvent As EventHandler
AddHandler(ByVal value As EventHandler)
_SomeEventListeners = [Delegate].Combine(_SomeEventListeners, value)
[Code] .....
When a delegate method throws an unhandled exception, that exception is usually trapped at the level of invocation (eg. Delegate.Invoke()) - you get a System.Reflection.TargetInvocationException...
However, when debugging classes utilizing a lot of threading/invoation, it would be helpful to be able trap the exception in the target method i.e. the faulty code, and since Microsofts BackgroundWorker (exceptions thrown in DoWork()) is able to do it, why can't I???
I need to create a monitoring mechanism using SNMP (in .Net). I think we'll be using an nsoftware component to handle most of the work. It appears we must use 'traps' to communicate from the agent to the server. We'll have a number of different traps and various information detailing each trap. What is the best way to implement custom traps? That is, what is the best way to not only send a trap, but also send the information describing the trap to our 'snmp manager'? I think this is done through "variable bindings". To use "variable bindings" do we need to create our own "enterprise number" and use an "enterpriseSpecific" trap? Should we implement our own, custom MIBs or can we just send the data we need with the trap (via variable bindings)?
This is the following. Normally, when i have a city, i'm using some javascript to autocomplete the cities as the user type. Now i want it to make it automaticly, using the edittemplate. So i would change :
I am using a loop to update properties of each object of a set of custom objects. The routine knows which controls to update because the controls value is not empty, I don't want the routine setting the corresponding properties to nothing when the control is empty. Now I know how to do this perfectly fine with IF statements such as:
CODE:
But this feels really redundant doing that same IF block over and over for each property/control combination, I thought about creating a separate routine that takes the control as an argument and does all the repetitive IF blocks but I don't know how I could also pass an object property to tell the routine to update that particular property.
So I've been doing some research on the singleton factory design pattern, and I am wondering if my example implementation is correct (warning I did get carried away creating animals):
I had been programming in Visual Basic 6 as an Intermediate programmer. I realized that it is far too old and is comparatively less powerful. So, I've upgraded to VB.NET. I'm using Visual Studio 2010. My query is before beginning programming with it, what things should I consider over VB6?
i am going to be saving data with DPAPI encryption. i am not sure whether i should just have one big file with all the data or should i break up the data into separate files, where every file is its own record. i suspect the entire dataset would be less than 10mb, so i am not sure whether it's worth it to break it down into about a few hundred separate files or should i just keep it one file?
it seems always at this time I cant figure out how to do something maybe it has something to do with lunchtime.
Im having trouble using a method that is defined by an outside company
This is a link to their integration guide:
[URL]
This is their documentation for the class Im trying to use
OrderQueryWebService Class
This class is for SID in particular and is made for use with the notification methods. This is for the Order Query Web Service specifically, allowing clients to return the status of transactions for their merchant, whenever they want to.
Methods / <summary> / Pass through the variables required and receive a list of Transaction objects showing transaction status
[Code].....
The MerchantCode, the MerchantUsername, the MerchantPassword are all good the List is a custom type called SetComHash.Transaction
Everytime I try adding a string to the list such as the transactionNumber and some other values it gives me a type error:
"Value of type string cannot be converted to 'SetcomHash.Transaction'
I am new to Visual Studio and Visual Basic, but I am a revived dBase, FoxPro, Visual FoxPro, ColdFusion programmer..I'm as good once as I ever was.So I am looking for how to implement some constants for the three main reasons anyone would want to use global constants:Readability, Maintenance,Memory Usage.For example in a list of error return codes, I may assign "File Not Found" an error code of 1010.To create a constant that exists only within a procedure, declare it within that procedure.To create a constant available to all procedures within a class, but not to any code outside that module, declare it in the declarations section of the class.To create a constant that is available to all members of an assembly, but not to outside clients of the assembly, declare it using the..Friend keyword in the declarations section of the class.To create a constant available throughout the application, declare it using the Public keyword in the declarations section [of] the class. global it is visible to all procedures and modules that comprise the application. Global variables and constants, as with Module level variables, must be declared outside of any procedures in the Declarations section and must use the Public keyword.The language above stating "Global variables and constants, as with Module level variables..." insinuates to me that Global Constants and Module Level constants are different, thus having different scopes.
And I have yet to see ANYWHERE that tells me to put stuff in the Declarations Section of a class or program or application, tell me just WHERE the declarations section actually IS! They always give the code of how to declare (I can do this...) but they don't say where the code GOES.I know I am overlooking the simplest of things, but just trying to be very sure of what I am doing.[code]
I recently downloaded VB 2010 Express so i am quite new to the language, but i have worked with dark basic, which seems to b very similar.Anyway, my problem is that i cannot seem to correctly set out my array of a custom type/class. i am trying to create two arrays, one of available entities and another of selected entities of which the user selects the entities to be dealt with in irrelevant ways. i have creates a button (called test) which adds some entities to the available list and all the entities come back the same value but they shouldnt be as you'll c in the code. i have run the step into command a found that "available.item(#).Name = " will change all of the entity's names.As of current i am working with lists as the array kept asking for a 'new' statement but i couldnt figure out where to put it.[code]
The intention is to convert an IList of custom objects to a string equivalent comprising each element in the Ilist. Unfortunately I can't seem to find a way to get the underlying data of the custom object, and of course as in the above example, using object simply gives me a string of types definitions, rather than access to the underlying data.
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?
What I've done is create a User Control Library (Project) and I've added a single User Control to that project. The control contains a single FlowLayoutPanel, and I created a Property on the control itself to pass the FlowDirection from the Control to its FlowLayoutPanel child.
Build, reference, component appears in the Toolbox and everything works fine, but the property on the control does not appear in the Properties window when I go to edit it at design time.
I need two seperate lists, which every item is Integer, String, Bitmap - and one which every item is Integer, String String. However I don't know how to do this, or even where to look - I've googled for custom objects and custom object lists. What I'm trying to do is this.Custom Object1 is Integer, String, Bitmap Custom Object2 is Integer, String, String
In one thread I'll be adding items to List1(Of Object1), and processing them, and adding the results to List2(Of Object2), however I need to be able from other threads to look at the list and say only give me the items where Integer = (my thread ID), is this possible? Any help, or even links to information that would be relevant to this request would be helpful?
I need a event that receives the position/location of an control, for example a Image-control, which i move with an animation.So I found some code from this post that I need, but I can't figure out where to put the code.Should I put it in some event e.g. the windows loaded event or what? What am I missing?
C#: var topDescriptor = DependencyPropertyDescriptor.FromProperty(Canvas.TopProperty, typeof(Rectangle));
I am creating an application which has n numbers of tabpages in three different tabcontrols. some of the tabpages are having graphs and rest of them are having some other calculations based on the data of focused graph tabpage.What i want is when user selects different tabpage containing graph the data of the graph tab should be passed to all the other tabpages using the data to calucate. There is one way which i get is to loop inside all the tabpages,but i want to raise an event from the graph page and handle the event in all the rest of the calculation pages.
I am trying to develop a VB .NET Windows Form Application FTP client that uses the C# .NET FTPLibrary.dll that I obtained from The Code Project article "A Windows FTP Client". I am also converting and using significant amount of the code from the article which, for the most part, I have been able to successfully convert to VB .NET using Developer Fusion's C# to VB code converter. The dll has a new message handler (NewMessageHandler) which is used in the article's main form (frmMain). There is a C# .NET statement in the SetFtpClient() method of frmMain that I am unable to convert to VB .NET. I have boxed the statement I need help with converting to VB .NET with " ===== " statements. [code]
I have a problem to handle an event on a custom control a have on a form.... So first i made a custom control that is just a groupbox with some labels and txtboxes. That control i add dynamically to my form like this (Baycontrol is the name of my control)
Declaration
Code: Friend Bay(29) As BayControl Add the controls to Form Code: For Simindex = 0 To 29 'Me.Bays - 1
I've got a page (aspx) that contains a usercontrol (ascx).On postback of the aspx, I'd like to read some control values in the ascx. So upon reading some good articles, I created an event in my aspx that fires on postback.The event handler is in the ascx, and simply writes the values I'm interested in to the viewstate so that the parent page can read them.The problem is my event handler never gets hit, even though I see the event is raised as I step through the code. So my code bombs when trying to read the viewstate (which is empty)[code]Oh, did I happen to mention I'm dynamically loading the ascx? :)
(using vb 2008 I am learning the workings of Custom Events. I think they might solve the problem of being unable to declare nonserialized events in vb2008. However, do custom events follow any sort of inheritance pattern like classes
I'm pretty sure i'm not doing this right but i hope by asking this someone can show me the right path.I've created a function that creates a label and 7 checkboxes arrays . So depending how many names i get from my database, it creates that many for the label and the other checkboxes.
Now my function is inside a module which i call in my Class Form during "Load".
So what i want to do is be able to code in an event where the user checks on one of these
I never did custom events and would like to make a sub procedure execute via a custom event from another form that does not have the custom event defined. For example I would like to raise the event from my ok button in one form and have the event in the other form execute. How to set this up using code examples?
Dim L As New Label AddHandler L.Click, AddressOf Labclick Me.Controls.Add(L)
I know how to do click events but how how do i make an event for it that does something when the mouse hovers over one of the Labels?for example if the mouse hovers over a label it changes text color to RED...when mouse leaves it changes back to BLACK?
I have a Windows Service project designed to monitor an email account and make entries into a SQL Server database when certain emails arrive. This is a rewrite of a similar winforms program that works just fine, except that it requires that the computer be logged into an account and the program started manually, which I can avoid by using it as a service.In the service I maintain a list of logged messages - basically just a string and a timestamp indicating that something has happened. (That list is shared out over a WCF service but I think that's immaterial, at least at the moment.) In my custom class I declare a public event, and elsewhere I raise that event. For some reason, though, the RaiseEvent isn't being run in the service. For example:
[code]...
The problem in this case is that _pc_HandleEvent isn't ever being called. If I duplicate this setup in a regular winform program, everything works like it should. What am I doing wrong? How do I get a service to handle events raised from other classes?
I'm writing a custom textblock control thats populate hyperlinks and raises event when clicked to hyperlink.
I wrote this code but I got stucked.
My code is :
Imports System.Text.RegularExpressions Public Class CustomTextBlock Inherits TextBlock
[Code]....
This code gives error at RaiseEvent Klik(sender, EventArgs.Empty)
Error is : Cannot refer to an instance member of a class from within a shared method or shared member initializer without an expliticit instance of the class.
I have an image of the political map of the USA. I want to write separate click events for each of the 50 states in Visual Studio. How would I do that?
I've been tinkering with Delegates, and now Multicast delegates. Every time I invoke two delegates It only displays one of the two delegates per invocation.
