How does one handle unhandled exceptions in a DLL? VS doesn't give me the option to add Application Events, I'm guessing because it's a DLL. Do I just have to do it in the main app?
View 8 RepliesAll of us use the try catch blocks. But what is the best way of handling errors within custom functions?Display a messagebox to the user when the exception is thrown (if possible within the function), or return a value indicating that an error was found within the function?
View 3 RepliesI have set up a process to create new tasks to handle file processing. A problem arised where I received and unhandled exception error and just clicking on the continue button, the main process continued to run. Now I also found that within the child task I was having a file conflict error and as the tasks run as separate .exe i was under the impression that everything would have been thread safe. So for the first issue here is the task creation in the main process..GProcess is a complete project on its own consisting of 6 classes. This is added as a class library reference to the main process class form1
Public Class Form1
..Private parser as GProcess.module = new GProcess.module()
dim factory as new taskfactory
[code].....
While I understand ApplicationEvents.vb won't catch exceptions in another thread, is there any reason why it shouldn't catch exceptions in the UI thread? From time to time I get exceptions that simply crash the program, even though an exception handler is defined as follows:
Private Sub MyApplication_UnhandledException(ByVal sender As Object, ByVal e As Microsoft.VisualBasic.ApplicationServices.UnhandledExceptionEventArgs) Handles Me.UnhandledException
[code].....
An application raises the UnhandledException event when it encounters an unhandled exception.
For instance, you can use this event to ask user send you a report by email.
[code...]
I read that if I put this code in ApplicationEvents.vb
[code]...
This was a difficult question to google. I have an Order class with a couple of dozen properties such as ClientReference, ShipMethod, etc. I use databinding to bind this class to an Order form. If a user enters an invalid shipping method, an exception is raised in the ShipMethod property and a validation error is displayed to the user. But I'm trying to use the same Order class within an OrderImport class whose job it is to take a flat file and create multiple orders. The problem occurs if I'm assigning to a dozen of the order fields consecutively, and say the first one causes a validation exception. If I have all dozen assignments occuring within a single try-catch block, the next 11 assignments will be skipped and I'll only be able to record one validation error. I could solve the problem by doing a dozen separate try-catch statements, but that doesn't seem very elegant.
View 22 RepliesWhat are some of the most common mistakes you've seen made when handling exceptions?It seems like exception handling can be one of the hardest things to learn how to do "right" in .Net. Especially considering the currently #1 ranked answer to Common programming mistakes for .NET developers to avoid? is related to exception handling.
View 14 RepliesIs there anything similar to the MyApplication_UnhandledException for an user control in VB?
I would like to have a central point where to catch all unhandled exceptions of a user control, without propagating the exception to the application that uses the user control. I made some test raising an exception in a method of my user control where there is no try/catch code (of course in the true project all methods have a try/catch block). The exception was caught by MyApplication_UnhandledException event of the application using the user control. But this is too "far" from the point where the exception happens and in worst case the user should restart the application.
I would like to realize a behaviour for the user control in order that if the user control fails, the exception is not propagated till the application, but just caught at user control level.
When two computers are connected through TCP, and one of them closes and breaks the connection, it throws error 10054 "Remote host forcibly closed the connection".I want to handle this error because I know it will happen more often than not with the application I'm building. In System.Net.Sockets.SocketException, there is an on the error code. But when I run the program, the exception that is being thrown is System.IO.IOException, and the GetType for IOException is the socket exception. I don't know how to handle the socket exception if it's not the root cause of the exception.
Here is the code for my Try Catch block:
For infiniteCounter = 1 To 2
infiniteCounter = 1
[code].....
If any directory within a set being searched by the [URL] or [URL] methods contains a junction point, the entire method fails and returns zero results on my tests under VB 2008. I would like to make the call more robust: to return the folders or files not blocked by access restrictions and to note the folders which were blocked. Do those methods offer a means to do this, or is a recursive folder-by-folder call necessary?
View 3 RepliesSo I've made this control that inherits from the treeview control and basically loads objects from active directory into a treeview (url...).All working fine, but as this is the first custom control I have made that I have intended for other people to use, I'm not quite sure how I should approach error handling.I mean, obviously I shouldnt do something like show any exceptions in a messagebox because that might not be what the person that is using the control wants to happen. So do I just write out exception messages to the debug window? Do I swallow exceptions (guessing not)? Do I just totally ignore them so that they are thrown in the user's project?
View 4 Repliesi created a Class library (.dll) and loaded it as reference into a main project. In the code for the class i've handled exceptions using try..catch subs, however when debugging the main project exceptions that are handled in the DLL still get thrown! (the class ".vb" file gets loaded into the debugger and the line of the exception shows up)
Up till now i've found it useful that when an unhandled error occurs in the imported reference, it shows up in the main project with tracing back to the referenced class. But i dont want the exceptions that are handled in the reference class to be thrown when debugging the main project!
As you can see the exception thrown was handled with try...catch this class exception.vb belongs to the project that created the class library (.DLL that i referenced). i didnt even load the project that built the reference so it amazes me that it could find the coding class to begin with.
I am writing a class library that envelopes an USB device driver. This device has its own class library, provided by the hardware vendor.
Very often, especially if you handle with old DLL or COM assemblies, there are methods (functions to be correct) that return TRUE if all was OK, or FALSE if any error happen. Often these methods return information about the error in one of their parameters or separately in a GetLastError method or even if in an OnError event.
Now, normally I handle all native .NET exceptions in my class libray handling locally or re-throwing to the client if the error is useful to know. But what to do with all other errors that are hidden in the vendor's methods? (in the true I have no exceptions, but only returned TRUE or FALSE values).
Let's make an example with the method "CONNECT" that connect the client to the USB device.
I envelope the method in this way:
Public Sub Connect()
oVendorDevice.connect()
End Sub
now if any connection error happen, the vendor's connect method return FALSE. But I do not know why the connection failed. To know why the connection failed I have to call (for example) the method GetLastError that gives me information about the error. (but do not forget that other vendors use other strategies like returning the error in a method's parameter or in a OnError events.
Now, in order to follow a good .NET exception handling strategy I could write something like this:
Public Sub Connect()
Dim res As Boolean = oVendorDevice.connect()
If res = False Then
[Code].....
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].....
I have an unhandled exception event in the ApplicationEvents area of my program, but it never gets called when I do get unhandled exceptions. Is there a trick to making this work?
View 8 RepliesQuestion: I catch generally unhandled exceptions with AddHandler System.AppDomain.CurrentDomain.UnhandledException, AddressOf OnUnhandledException
The problem now is, with this exception handler
[Code]...
Question: I catch generally unhandled exceptions withAddHandler System.AppDomain.CurrentDomain.UnhandledException, AddressOf OnUnhandledExceptionThe problem now is, with this exception handler
Public Sub OnUnhandledException(ByVal sender As Object, ByVal e As UnhandledExceptionEventArgs)
Console.WriteLine(e.ExceptionObject.ToString())
[code].....
Part of my assignment is to check if input to Group Number and Number of Units are correct input by making error handling exceptions...
I have to check the following:
a) group number is neither 501 nor 062
b) number of units are NOT numbers
c) number of units is NOT a positive number
So my first question is, am I checking correctly? 2nd question is, How do I make sure my Exceptions will pertain to their correct respective things (a, b, and c.. above)?
[Code]...
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?
View 1 RepliesSince reinstalling VS2010, it has not been displaying proper debug info. I don't think I changed any settings but I have had a hunt through the options and can't see anything I might have messed up. I have had a quikck search and other people seem to have had the same problem but no solution. I'm running Windows 7 x64 with latest updates, if that matters.
View 1 RepliesI used the following code(with bug):
Code:
For n = 0 To 100
If saveLine(n).Substring(0, 8) = "heading:" Then
cboSelect.Items.Add(saveLine(n).Substring(8))
End If
Next n
The For loop only ran 5 times. It turned out that saveline(5) was shorter then 8 characters, so I changed the code which solved the problem:
Code:
For n = 0 To 100
If saveLine(n).Length > 8 Then
[code]....
VB 2010 neatly exits the for loop when the bug occurs. In this case it was easy for me to pick up the bug, because the combo box was not properly populated. What if it was not obvious that the for loop did not complete? It is quite scary to think that bugs like this are not displayed at run time.
Anyone out there who happens to have an exhaustive code snippet for SEH (including all possible exceptions) for VS 2008 or VS 2010 (.NET 3.5 or 4.0) ?
View 10 RepliesI have a sub which creates an XML file but the thing is, all the parameters are 'hardcoded', so I decided to give some inputs so each data in each node is customizable. Now, I would like a loop to read the text in textbox1 and assign that to variable one, do the same for textbox2, write the node, loop again (using the same variable) and assign that variable a value in textbox3 and write the node.
I can while loop to write nodes, but only for fixed data or data with 500000 variables for each loop. Is there any way to do this such that on each loop it dynamically sources the variables data from the 'next text box'. i.e. One first loop uses textbox1, second loop it knows it has used textbox1 .'. it uses textbox2 etc... Is there a way to do the same thing but write back to text boxes in an order, knowing what was previously written.
I am trying to add some error handling for AppActivate if any error occurs.I initially tried using a try statement and cancelling the sub that calls the function where my AppActivate code is, but that didn't work.I have tried looping it, changing values and everything I know. I have Googled and nothing :S
Here is my I have removed all the error handling I tried to implement, however, this commented msgbox I would like to be included (that is, possible to execute) in any methods you present.
[Code]...
i am creating ovalshapes during runtime....and i want to trigger an event when its clicked,an array a(5) is declared as ovals
View 2 RepliesI'm trying to manipulate the events of the dataGridViewComboboxColumn in order to execute an SQL statement based on the value change of the cell (IndexChanged) and update the database table. Either this or how can i update several rows in a table from a datagridview ? if you check my previous posts you'll understand the whole story behind this question and to which grid i'm refering to.
View 2 RepliesI took a VB class a couple semesters ago and I did really well. Unfortunately, it seems as though we only covered the very basics within the class, as I feel rather clueless right now.
Here's my issue. I'm trying to write a program that will encode notes (like music notes, A-G#) which are entered by the user, into digits, 0-9. Now I have the system laid out, in that 1-8 will represent A-A, while a 0 or 9 preceding a digit will represent a flat or sharp respectively.
Now my question is actually rather basic, but I just can't seem to figure out how to do this. The user will enter the note sequence by clicking on buttons (12 of them). What I'd like to do is create one sub that will handle all possible button clicks. I suppose it's possible that I could have separate subs for each and every button; but it just seems more efficient and cleaner to have one sub that manages them all.
The part I have completed and working properly will display a message (the same message) in a messagebox each time any of the buttons are clicked. So I have the "Handles" part working for all 12 buttons. But what I'd like to do is write code, perhaps "If" statements such that If "btnA" is clicked, then say "You clicked Button A," and If "btnASharp" is clicked, then "You clicked Button A Sharp," and so on. Is it possible to do this somehow by recognizing which event was actually triggered?
I am trying to make a UserControl or Component which can be dragged from the Toolbox onto a container control such as a Form or a Panel. Its purpose is to change the behaviour of that container. In particular, I would like to add functions to the container's painting and mouse actions. I DO NOT want to have to write code for the container itself -- that's the whole point of the Toolbox object.
I can do this by getting a reference to the object's Parent (or Host in the case of a Component) and handling its events, as this example illustrates:
[Code]...
However, I have heard that handling the events of a parent control conflicts with OOP principles. So I would like to know, does that objection apply in a case like my example? If so, what are the drawbacks? And what alternative techniques are available?
I was just wondering if it is considered overkill to add:
[code]...
To every sub in your project. And what would be the side effects of this if any.