C# - Implement A Handler Method For Exceptions Correctly?
Jul 5, 2011
Suppose I have the following construct:
Public Sub SomeMethod()
Try
doSomething()
Catch ex as Exception
[code]...
And I would like to write handleException(ex). Suppose my class has different options of handling events:
Public Enum ExceptionHandlingType
DisplayInMessageBox 'Display in msgbox
ThrowToCaller 'Raise the error to the caller routine
[code]...
Below is my attempt at writing "handleException". It seems no matter what I do, if the object was set with Exception mode of "ThrowToCaller" then the stack trace gets all messed up when I use handleException(). How can I just have a clean stack trace generated when the option is "ThrowToCaller" (every other option seems like it is working fine)
Public Sub handleException(ex as Exception)
Select Case mExceptionHandling
Case ExceptionHandlingType.DisplayInMessageBox
MsgBox(ex.Message)
[code]...
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Sep 8, 2011
I have a requirement for a timer that has the following behaviour:
Millisecond accuracy I want the tick event handler to only be called once the current tick handler has completed (much like the winforms timer)I want exceptions on the main UI thread not to be swallowed up by the thread timer so this requires Invoke/Send instead of BeginInvoke/PostI've played around with CreateTimerQueueTimer and had some success but at the same time had problems with code reentrance and/or locks when deleting the timer.
I decided to create my own timer so that I could get a better idea of what is going on under the hood so that I can fix the locking and reentrance problems. My code seems to work fine leading me to believe that I may as well use it. Does it look sound? I've put in a check if the timer is deleted to make sure that the deletion is complete before the timer can be created again. Does that look ok?
Note: I should say that I call timeBeginPeriod(1) and timeEndPeriod(1) inorder to achieve the millisecond accuracy.(The following code is converted from vb.net to c#, so apologies for any missed mess-ups}
ETA: I've found a problem with it. If the timer is running at an interval of 1 millisecond, and I call, say, Change(300), it locks up @ while (this.DeleteRequest). This must be because the TimerLoop is in the this.CallbackDelegate.Invoke(null) call.
[Code]...
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Jul 29, 2009
I decided to get my head back into VB. My question is ; how to I correctly implement a Call procedure? I cannot seem to find a simple example through google.
for instance :
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim selectString As String = Nothing
[Code].....
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Oct 31, 2011
I have a linq query which loads approx. 1000 lines into a variable, during that process I want to display a progressbar, not necessarily stating the percentage, can be marquee style, doesnt matter.
This progressbar is on a modal form to precent the user from interacting with the app for the time the query's running.
[Code]...
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Oct 19, 2011
I would like to catch any exceptions from any method in a class so that I may record class specific data to the exception for logging before it is passed up the stack. I know that I can put a try-catch in every method of the class, but there are many methods and It seems there should be a more efficient way. Example of what I am currently doing:
public class ClassA
{
private int x;
[code].....
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Jan 14, 2009
When I've used the remove handler method in my code, I get this warning:The 'AddressOf' expression has no effect in this context because the method argument to 'AddressOf' requires a relaxed conversion to the delegate type of the event. Assign the 'AddressOf' expression to a variable, and use the variable to add or remove the method as the handler.Why do I have to assign the "AddressOf" expression to a variable?
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Apr 20, 2012
When you click on a button control on a web form visual studio automatically put in this code for you in the code behind.
Protected Sub btnSave_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btnFlightInfo.Click
end Sub
Say for example, I wanted to call this method from another method. How would I do that? I know that the sender is the actual button object, but what is e? Here is what I have so far inside another sub. Just trying to get a better understanding of how this method works.
btnSave_Click(btnSave, ??what would you put there??)
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Mar 17, 2012
I've already asked this question on several forums, but without any good explanation of why the code above cannot be converted from C# to Visual Basic. The code is actually from this forum, written in C#. (the source)
[Code]...
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Nov 10, 2010
I want to implement an extension method in VB.NET that will clone an object of type T.Say, I want
Dim cust1 as New Customer() //...
Dim cust2 as New Customer() //...
cust2 = cust1.Clone()
[code]....
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Jul 4, 2009
With reference to my previous thread on Paint event handler.. [URL] I went to read up more on Paint Event Handler.. I have a button which draw out a path based on the user selection.. Below contains the drawing of the path portion of the button click event code
[Code]...
However It did not activate the paint event when I clicked on the button.. Instead, the paint event still activate even before I click on the button? So can anyone teach me on how to activate the paint event when I click on a button?
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May 14, 2012
I need to implement caching in Asp.net web application My need to store data with different ID's. So which method is better ?
Use a dictionary variable. Insert the data (key as ID and data as value).
Dim mDict As New Dictionary(Of String, String)
mDict .Add(bID, uwtTree.WriteXmlString(True, True))
Cache.Insert("mTree", mDict)
[Code]....
Which method is the best way ? Or is there any other method exists ? I am using .Net 3.5 /IIS 7 (VB.Net).
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Feb 8, 2011
I'd like to implement a common method on most of the forms, but not all.Let's call the method 'FormCleaner'.
I'd like to recursively call each forms FormCleaner method and ignore cases where the form has no such method.[code]...
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Jan 13, 2012
I have the following
Private Structure FadeLabel
Dim Alpha As Byte
Dim Color As Color
[CODE]...
Which I picked up from this thread: [URL]
What I'd like to do is 'implement' the BringToFront method so that when I use the 'FadeLabel' structure I can also call it's method 'BringToFront'.
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Mar 15, 2008
I'm binding a DataGridView to a BindingSource to a LINQ IEnumerable, I found that the BindingSource.Find method throws an exception because .Find isn't implemented in IEnumerable (and the BindingSource just passes the call to it's DataSource). I need to use BindingSource.Find to select/highlight a particular row in the DataGridView.
Is there a feasable way to extend my DataContext to support this behavior w/o breaking anything else? I expected to find the code out there already, but I've searched exaustively with no luck.Without it, I cannot "move" the BindingSource using .Position and that's a pretty common use of the BindingSource I think.
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Dec 26, 2009
I've just skipped around a few inbuilt VB classes' methods which throws exception. of all that i've came across, methods may throw multiple exceptions but ALL of them are exclusive, meaning there is no way 2 exceptions will ever occur simultaneously, yea and i was trying to make my class throw 2 exceptions simultaneously, hence this question, must all exceptions be exclusive?
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Mar 30, 2009
I am trying to calculate the number of years for my calculate age event handler, however i am apparently missing a method or whatnot because im trying to calculate the age , can anyone suggest help on this. I need to subtract years to get my age but when i try the birthdate.Subtract (currentDate) method i get an error about not able to convert from LONG?
So below is what I have.
Private Sub btnCalculateAge_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculateAge.Click
Dim currentDate As Date
Dim BirthDate As Date
Dim Age As Long
[CODE]
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Oct 9, 2009
Error1Option Strict On does not allow narrowing in implicit type conversions between method 'Private Sub searchResult_SearchFileMatches(sender As Object, e As Jam.Shell.FileMatchEventArgs)' and delegate 'Delegate Sub EventHandler(sender As Object, e As System.EventArgs)'. on RED Text
[Code]....
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Oct 19, 2010
Consider a MyForm class that contains a shadowed implementation of Show(). It also contains a CreateForm() method, which accepts an instance of the form and calls the shadowed sub:
[Code]....
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Aug 27, 2011
How do I get a Event Handler to fire from within a nother Event Handler?
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Apr 18, 2011
The event handlers in my parent class are never called though the events are raised in the child class.
The Code:
Public Class childForm
Public Event checkboxchangedEvent(ByVal checkbox1 As Boolean, ByVal checkbox2 As Boolean)
Private Sub checkboxchanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged, CheckBox2.CheckedChanged
[code]....
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Mar 21, 2012
remove an event handler from within the event handler?
I have a class that gets data from a hand scanner. When the scan is complete and the data is validated, the class fires a custom "ScanComplete" event and returns the data in a custom EventArgs.
In the calling program, I'm creating an instance of the scanning class and adding a handler for the "ScanComplete" event. In the event handler I get the data that was scanned and then remove the handler.
It seems to be working but it feels wrong to remove the handler while I'm running inside the handler. Will this cause a problem?
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Apr 30, 2011
I need to write a program that indicates the larger of two variables using exceptions.I'm not sure if this is an acceptable code. I'm new at this and attempted with this code here:
[Code]...
I normally wouldn't use an exception but I am asked to use one, I'm just not sure what kind of exception would work best.
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Oct 24, 2010
I'd like some advice on building in known errors. Let's say I have a Windows form that needs to set the source path of an image in an object. It must be:
A valid path
An image
A PNG
[code].....
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Sep 11, 2009
I have a class that has a method A and a helper method B, method A internally calls method B. method B throws few exceptions to the caller also method A throws it's own exceptions, Assume method A throws "NotImplementedException" and Method B throws "SQLException", in the XML of each method, one which method that should put "NotImplementedException" and "SQLException" in <exception cref></Exception >
Should i put both exceptions on the XML of method A?
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Apr 6, 2009
I'm working on an ASP.NET web application, written using Visual Basic, and I'm trying to track down an error message that I'm getting.I'd like to get it to log the exception to a file (or the event log) so I can see it, as the error only occurs on the production server, and not on the development environment (therefore VS isn't installed on there...).
Does anyone have any thoughts as to best practice as to how to do this ?
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Dec 25, 2010
Why is the net filled with examples like this? Why do people just chuck try catch around any expression with out the slightest thought about pre-validation?
i would never just add try catch and not handle the exception. I tell people this is basically on error resume next in disguise.
Is an exception ever unimportant to just use try catch but with out any message?I really want to progress as a programmer but have i been approaching all this wrong?
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Sep 15, 2010
But what if you can not think of the exception that could be thrown?for example
Private Sub ListCurrentlyRunningProcesses()
Dim ActiveProcesses() As Process = Process.GetProcesses()
Try
[code].....
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Jun 10, 2009
When you use Try Catch for Exceptions, will
Catch ex As Exception
Catch any possible error that could occur or do you have to catch each exception separately?
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Feb 4, 2011
Is there a way to catch these Exceptions? (I am not looking for "just put try/catch or on error goto around them"). I am trying to find out if these errors can be caught by something outside of them.[code]...
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Jan 7, 2010
I have a project that runs perfect under windows xp. Now I have tried to run it under Windows 7 and got there a lot of exceptions under Immediate window.
A first chance exception of type 'System.ArgumentNullException' occurred in Microsoft.VisualBasic.dll
A first chance exception of type 'System.IO.FileNotFoundException' occurred in LP_Wizard.exe
[CODE]...
What wrong with that Microsoft.VisualBasic.dll in windows 7 and how i correct that problem ?
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