Displays One Of The Two Delegates Per Invocation?
Mar 27, 2011I'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.
[Code]...
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Debugging Exception On Invocation Target Instead Of Invocation Caller?
Jan 28, 2010When 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???
Delegates And Multicast Delegates In .NET
Mar 27, 2009What are Delegates and Multicast Delegates in VB.NET? How do I use them? provide a simple example to illustrate the concept.
View 1 RepliesException Has Been Thrown By Target Of An Invocation.
Jan 15, 2012I'm working on an application that contains a "BackgroundWorker", the "BackgroundWorker" worked fine but after I started to change some stuff it gives me an error ("Exception has been thrown by the target of an invocation.")... I used a breakpoint to see where it happens, the exception gets thrown at the "End Sub" line of the BackgroundWorker.I then deleted all the code inside of it and ran it again.I still get the error.
View 12 RepliesException Has Been Thrown By Target Of Invocation
Feb 27, 2009What is the meaning of this error message?
"Exception has been thrown by the target of an invocation"
Instead of words, here is my code's logic :
while loop
run BGworker01
run BGworker02
...
run BGworker09
application.doEvents
thread.sleep(10)
end while
All the bgWorkers do the same thing (sending some data, only to different locations). When I run this loop with only 1 Background-Worker, it's all fine, but when I add the other bgWorkers i get the mentioned error at the "application.doEvents" part of the loop. I think it also points to another place (highlighted in green) inside one of the bgworker's code :
Dim FileStreamToSend As FileStream = New FileStream(fileToSend, FileMode.Open)
I thought it might be a problem that all bgWorkers are trying to read from the same file together, but when I tried using different file for each bgWorker, the problem persisted.
Exception Has Been Thrown By The Target Of An Invocation
May 28, 2010I want to use mozilla control in my application.. But when i use Webbrowsercontrol i just use
webbrowser.navigate("http://www.google.com")
but this commant is not working with mozilla control ant when we try to navigate to any web address it gives following exception.
Exception has been thrown by the target of an invocation.
Exception Has Been Thrown By The Target Of An Invocation?
Jan 21, 2011I know this is a relatively common error but I am working in an application that allows custom reports to be written using vb.net or C# for scripting. Error handling is very poor and I am not knowledgable enough to add my own (if it is even possible).
My code simply retrieves a value that is stored in a textbox on the report formatted as LastName, FirstName and truncates all characters after the comma. This value LastName is placed in a new textbox on the report. Here is my code:
Sub Detail1_Format
Dim lastNameFirstName As String = ""
Dim lastName As String = ""
[Code]....
The error happens when I use lastNameCommaIndex to set the number of characters in my substring. If I replace it with a number the report is published properly.
VS 2005 Invocation Exception Using AutoResetEvent?
May 16, 2009I am using a background worker to process some login information. However, the background worker has to stop and wait for 2 events to happen. Once these have finished the background worker can complete its job. They are callback that will call the Set() method of the AutoResetEvent.
So I am using AutoResetEvent to set when these 2 events have finished. However, I seemed to be getting this error message
"Exception has been thrown by the target of an invocation." and Inner exception
"Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index". The exception usually fires when the registration success leaves scope.
The code for the background worker.
' Waiting for 'Account in use' and 'Register success or failure'
Private loginWaitEvents() As AutoResetEvent = { New AutoResetEvent(False), New AutoResetEvent(False) }
[Code].....
Backgroundworker Exception Thrown By The Target Of An Invocation?
Jun 21, 2010Currently I m working in backgroundworker .but suddenly it begins to throw an exception
Exception has been thrown by the target of an invocation. source:mscorlib
stack trace :at System.RuntimeMethodHandle._InvokeMethodFas
WinForms : Exception Has Been Thrown By The Target Of An Invocation?
May 21, 2010I have a winform where I have some controls like TabPane, Label, ....When I launch my application without localization, it works fine. When I put localizable parameter True, I have this error :
TargetInvocationException was unhandled
Exception has been thrown by the target of an invocation.And when I debug my application, I follow the execution, program begins executing InitiliazeComponent(). I press F11 to continue the debug, program executes the TabIndex event of my TabPane and on the first instruction it crashes.My environment is VS2008, Framework 3.5. I store my project on a network hardisk (I test on local and it doesn't work too)
Custom Event - Invocation List Implementation Considerations
Apr 9, 2010I'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] .....
Delay - Receive A Target Invocation Exception Error
Jan 13, 2009I am creating a programming that is sending info for one pc to another over RF. The desktop show create a xml file. It writes some of the info but not all. I receive a Target Invocation Exception Error. I realize I need to slow down the incoming Data. I want to use a timer to slow it down.
View 4 RepliesError Message: Exception Has Been Thrown By The Target Of An Invocation
Oct 1, 2009It errors often (not in a system damaging way) but enough that it bothers me.
Code
Public Shared Sub Fire(ByVal thisEvent As [Delegate], _
ByVal ParamArray args() As Object)
[code]....
Common Error
User Message: Async event fire error.
Error Type: System.Reflection.TargetInvocationException
Error Message: Exception has been thrown by the target of an invocation.
[code]....
Dynamic Invocation Of Methods In DLLs / How To Change Method Signature
Dec 27, 2011I am using some interesting code to perform dynamic unmanaged dll calling:[code]I want to be able to change the parameter signature and type of the delegate to void or to a function returning integer, string, or boolean.Basically, I want my program (interpreter) to be able to call upon any method in any unmanaged dll that the programmer has access to since I cannot predict what method the programmer will want to have access to - I'd like to enable them to have access to any useful method.[code]This raises a complaint on the line with 'Dim theResult = ' on it. The error is "Object of type 'System.Int32' cannot be converted to type 'System.Object[]'."
View 1 RepliesWaveout Sometimes Memory - Output A Piano Tone Using Winmm.dll Via Platform Invocation Services
Feb 23, 2010This code works to output a piano tone for 2 seconds using winmm.dll via platform invocation services, it seems to work fine on XP but waveoutopen fails in windows 7 rc updated based on feedback from John Knoeller
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XML Serializing Delegates
Feb 10, 2010I have a class that I want to be serializable but contains a public instance of delegate that, apparently can't be serialized: [Code] Is there a way to make it serializable however?
View 4 RepliesConstrain Arguments NOT To Be Delegates?
Feb 3, 2012Consider these two functions[code]...
My question is: what is the right way to accomplish this to resolve the ambiguity so that I can pass value or references types and get overload 2, but pass Functions and get overload 1? Can I constrain the types in some way to make this happen?
Extra Variable For Delegates?
Feb 17, 2011[Code]....
So func is a function that accepts a string and return a string. In practice, internally, func also utilizez text1, text2. In fact, func can even be a member function with access the object that owns it (something like me or this operator).
And all that can be accomplished without changing the signature of func? How do the compiler do this?
GetCustomAttributes And Generic Delegates?
Dec 15, 2010I am struggling to get the syntax for the reflection call GetCustomAttributes ... at least I don't seem to be able to get hold of the custom attribute which I've decorated a particular method with. The complicating factor maybe that I have passed that method into an extension method as a generic delegate. (The other, more likely, complicating factor is that I'm not sufficiently familiar with reflection or what happens when you pass a method as a parameter like this!)
The code appears to run, and when I step it, the count returned from the GetCustomAttributes is 1. I can't work out how to get hold of that custom parameter
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Interface Of Multiple Delegates?
Nov 29, 2009is there a way to create an interface of delegates? Sub dostuff(byval arg1 as dele1)works, problem is that i have 8 delegates, so i will have to give it 8 signatures. that isn't so bad, but the problem is that when there are various combinations of signatures it gets real real bad.
Sub dostuff(byval arg1 as [Delegate])works, but it allows me to accept delegates beyond the 8 that i wanted (it's like declarign arguments with base Object)could i be able to do this:
Sub dostuff(byval arg1 as Idele1to8)
Lambda - Anonymous Delegates In .net (pre Vb9)?
Apr 7, 2009Is it possible to create anonymous delegates in vb.net version 8 or earlier? If so, could someone provide an example of the syntax?
View 2 RepliesMultithreading Or Delegates With WMI Calls?
Jul 12, 2011I have a VBNET app to scan my Active Directory using WMI calls and return some basic informaiton such as Dell Model name, current user logged on, Dell Service Tag etc my issue is the app becomes unresponsive whilst it scans and i have to wait for it to finish looping before i can work with it, in the past a do events used to suffice
I think Multithreading is the way i may need to go, whats the best approach? I tried to use Delegates but it doesnt seem to have made any difference
below is my for next loop code that calls the functions, the last section "Private Sub Button1_Click" down is the Delegate code i attempted
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Specify Generic Types On Delegates?
Nov 15, 2010Maybe I am just not reading the MSDN documentation correctly, but given a function that takes in one string parameter and returns type T, how can this be specifed as a shared function using Func()?
MSDN says Func(Of In T1, Out TResult), but all of their examples use the same data type, i.e., Func(Of String, String). I want to do Func(Of In String, Out T), where T is arbitrary (but I can constrain it if necessary by a base class). I want it shared/static at the class level, yet the encapsulating class will itself not be a generic class. It seems in this specific scenario, it's impossible to do what I want because the compiler would have no way of knowing what Type T is at runtime.
So is it possible to do generics on delegates or anonymous lambda expressions in VB.net (not C#)?
Use Delegates For Handling An Event?
May 7, 2009I can come up with, if I understood the solution better, I could probably phrase a better subject line.[code]...
View 2 RepliesVS 2008 Delegates And Backgroundworker?
Jun 4, 2010I am having trouble with getting a delegate to work properly.Here's my
[Code]...
What Is Difference Between Delegates And Events
Feb 11, 2010What is the difference b/w Delegates and Events. I have little bit confusion. Where delegates are used, and when we have to used delegates. Can, you give some examples(both delebates and events) in vb.net.
View 6 RepliesWhy Are Event Delegates Required
May 26, 2009I was going through tutorials and found the topic of Events and Delegates. However, I fail to understand why should this be required ? Instead of having to raise events, can't one just call the necessary procedure ?Sorry for posing this basic question. Any replies or even links to existing posts are welcome. [Also not sure if this question strictly falls under VB.NET category.]
View 4 Replies.net - Utilize Optional Parameters In Delegates?
Aug 6, 2010However, I am wondering if there are any workarounds or plans for incorporating this feature into VB.NET in the future?What I'd like to do:
Public Delegate Function Deserializer(Of T)(ByRef Buffer() As Byte, optional ByRef BufferPosition As Integer = 0) As T
'Implementation of a func that matches the delegate'
Class A
Public Function Deserialize(Byref Buffer() as Byte, optional Byref BufferPosition as integer = 0)
....
In the absence of specifying "optional" inside the actual delegate itself, it'd at least be nice to be able to do it in the function implementation only:
Public Delegate Function Deserializer(Of T)(ByRef Buffer() As Byte, ByRef BufferPosition As Integer) As T
'Implementation of a func that matches the delegate'
Class A
Public Function Deserialize(Byref Buffer() as Byte, optional Byref BufferPosition as integer = 0)
....
At least this second way, the functions for the delegate will always have a value mapped to each parameter, although some may come from the function side and not the calling side.
Checking How Many Delegates Are Attached To An Event
Jan 30, 2010is there a way to check how many delegates are attached to an event, let's saymybutton.Click has 10 handlers, 5 by using the Handles keyword and another 5 added by using the AddHandler method (well this is not the point, then point is that i do not know how many handlers there will be). and i would want to create another button that had all 10 handlers of mybutton.Click attached to its Click event as well.
View 6 RepliesDataReceived Event And Delegates Reference?
Dec 3, 2009I'm looking for a reference that can explain the concept and use of the DataReceived event and Delegates subject.The reference has to be pretty simple as I'm an "old dog attempting to learn a new trick". I'm not ignorant of things programming, but am ignorant of things dealing with serial communication in VB2005.I already have a couple of O'Rielly books ("VB2005 Cookbook", "VB2005 Desktop Reference") and I have a book that deals with serial communication from a Jan Axle-something. Neither O'Rielly books have any info, and the Axle-someting book's remotely related examples are too confusing for this slow learner.
View 6 Replies