Question Guidelines To Handle Exceptions In A Class
Feb 26, 2012
I created a custom collection class with some methods: each of these has some parameters and throws an exception if a parameter is not valid.For example, the Add and Remove methods throw an NullReferenceException if one of their parameters is null.[code]...The Replace method replaces an item in the collection with another specified object: to reach the goal, it first calls the Remove method and after the Add method. Obviously the Replace method could throw exceptions if at least one of the specified parameters is null, because Remove and Add methods could throw exceptions.Is this the right way to go? Or should I also check the parameters in the Replace method as in the following code? [code]...In fact, in this second case, each check would be executed twice: first in the Replace method and after in the Remove and Addmethods, which are called by Replace, and in other cases the checks may be rather expensive.
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Apr 1, 2009
I have a SqlDataSource that is supplying data to my GridView. Thats all i am using on my form, thus i have NO code behind at all. But somewhere i need a TRY CATCH block just in case my connection get's lost. What code must i place where?
If i get a error i want my lblMessage Text to be "No connection".
Edit
My GridView in my Machine.aspx
<asp:GridView ID="GridView1" runat="server" AllowPaging="True" AutoGenerateColumns="False"
Height="209px" PageSize="7" Width="331px" AllowSorting="True"
[Code].....
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Apr 2, 2009
I was reading a couple of articles a while back which I think described a behaviour where you can, in a .net application (specifically VB.net), allow an exception to occur, and then handle it in some kind of application-level exception handler, as opposed to within a Try/Catch block. My google-fu is weak at the moment, so I'm not having much luck guessing what this feature is called in order to find information about it.
[Code]...
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Aug 20, 2011
I am working on a .Net Remoting project. If there is any exception in remote object, I would like to send this exception in detail to the client. I am using the following code to accomplish that-
'This is on a shared .dll
Public Interface ICreateNewMouza
[code].....
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Jan 22, 2009
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...]
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Dec 28, 2009
Is it possible to handle exceptions on the AppDomain.CurrentDomain.UnhandledException callback? I want to do the following:Show my own "an exception hasoccured" dialog, with a "Send Report"button After the user dismissed thebox, I want to close my app, but I donot want to Windows default crash dialog "Theapplication needs to close" box toshow up.
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Apr 11, 2012
Is there a way I can catch and handle two different exceptions within the same exception type? For example:
Try
' My code
Catch ex As System.Net.WebException
End Try
I have 2 different exceptions that are System.Net.WebException. I want to handle them different ways. Problem is the catch block above catches them both. Is there a way I can determine if which of the two it is and handle them differently?
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Dec 27, 2011
I have a relatively simple VB.NET app. It targets framework 2.0 from Visual Studio 2010. The app works fine most of the time, except that the users sometimes receive the
following exceptions. The error is completely random and somewhat rare. I haven't been able to trap it while in a development environment. It also doesn't appear to be
pointing at my code. My app continues to run if the users ignore the error. How would I trap and handle this error?
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Jan 31, 2012
I wonder how to use statement handles exceptions?Do I need to wrap the using statements with a Try/Cath/Finally clause in order to be sure that the SqlConnection object is closed and disposed even if the containing code throws an exception? [code]
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Dec 6, 2009
I'm creating a class library that contains a series of functions with Try...Catch blocks to handle errors. When i run another application that uses the class library, and call a function in the library using parameters that i know should cause an error (i.e. divide by zero), i don't get an exception thrown.
Can you not use Try.. Catch blocks in external libraries? If not, how are you suppose to handle errors in these functions?
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Jun 8, 2010
i 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.
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Apr 14, 2009
I have a "partial" class in VB.NET. Half of it is auto generated by a code generation tool. That half implements INotifyPropertyChanged, so any properties in that part of the partial class raise the PropertyChanged event.In my "custom" part of the class, I declare another property that depends on one of the properties in the auto-generated side. Therefore, when that auto-generated property changes, I also want to raise a PropertyChanged event on my custom property that depends on it.
If I go into the generated part of the class and raise the event there, that will get overwritten if I ever re-generate that part, so I don't want to do that. I would rather add an event handler in my side of the partial class that checks if the generated property changed, and if so, raise another event for my custom property.
[Code]...
I'm assuming it's because normally you'd use the WithEvents keyword to tell the compiler that you're subscribing to events from that object. I don't have a clue how to do this inside of the class that's actually raising the event, or if that's even possible.
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Sep 28, 2011
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].....
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Oct 15, 2007
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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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Jun 15, 2012
We develop small applications for various customers. I now got a task to set up some coding guidelines for in-house and external programmers. (Management know nothing about development and only see the problem in transferring projects from one developer to another. Customers pay by the hour and development is a small part of total project so code quality is a non-issue)My first step is to set up guidelines for C# and VB.Net (SQL will probably come later).(Most code here is created with CTRL-CCTRL-V and testing is done with F5.I have tried to introduce unit testing / code review but that is not going to happen. Static analysis is the only way forward at the moment)I am most comfortable in C#/C++ (but sometimes work with existing VB6/VBA/VB.Net code) so setting up C# guidelines is pretty easy: [code] For VB.Net I need to replace StyleCop with some written guidelines but how do I set up the VB.Net compiler.Personally I never code without Option Explicit / Option Strict etc but if I do that on our VB.Net projects I get hundreds of warnings/errors (implicit conversions, default return type/value etc).The VB developers does not seem to have a problem working without help from compiler warnings. I do not think their productivity generally differs from C# developers (it is more a personal thing).I do not want to enforce my own preference for static checking so my questions is: What warning levels are reasonable/best practice for VB.Net development?
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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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Sep 2, 2011
I'm trying to move some code into some class files to clean up my code. One area I'm having trouble with is reporting progress for events between the object performing the task and a progress bar. I guess the event functions have to be placed in the new class but they also need to update the progress bar on the calling form? Can the classobject return updates in place of the event handlers?
[Code]...
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Nov 13, 2009
i have the ComClassSearchCustomers class and interface IComClassSearchCustomersat .net which used to create a tlb file. The class raise an event inside new. After that i have a vb6 form Form1 which catch the event , but it never see the event.
[Code]...
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Aug 21, 2011
I'm converting a pretty large chunk of code into a Class so that it can be re-used more easily, but am having a problem with one of the Methods. I have a method that uses the following line:'GET HANDLE OF ANY POPUP WINDOW ASSOCIATED WITH MAIN FORM [code]The "Me.Handle" part won't work, but I don't know what to replace it with so that it knows to use the handle of the main application's form that is using the Class.Do I need to get all Process that match my application's and store the Process' handle?
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Jul 14, 2010
I am attempting to share a sub menu among several different parts of an application so that it is consistent (not wanting to copy/paste.) I thought it would be simple. I am doing something like this:
[Code]...
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Feb 22, 2010
if I wanted the button onclick event in a different class how would I declare it?
when I refer back to the form it says I need to declare with events..
Private Sub btnAddToLaneFilter_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Dispatch.btnAddToLaneFilter.Click
If Me.txtCriteria.Text = "" Then
[Code]....
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May 3, 2012
I'm writting a class that needs the form handle but there is a way to use it without send it as argument in the class constructor or in a property?I know that the handler is not set until the form is completely loaded so that is another problem too.The basic idea is catch the form handle without pass it as argument and handle the wm messages.
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May 3, 2011
I have a table called ConcernedParty. It has an ID field, description and a TypeID which is a foreign key to the pk TypeID column of a table names ConcernedPartyType.Now i'm creating two classes. One for each table. In my ConcernedParty class I have and ID, Description property etc. how must I handle the TypeID in my ConcernedParty Class.
Do I declare it as:
Public Property TypeID as ConcernedPartyType
Or
Public Property TypeID as Integer
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Feb 24, 2012
I've been searching for the answer for a while but can't find it yet. Basically so far I have a simple VB.Net form with one button.I would like to make a class or module that can handle events from the main form. This is my code so far but it doesn't seem to work.
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Oct 17, 2011
I want to use One routine to handle multiple events & i want to give the list class object to the routine handle clause in vb.net. Is it possible? I have 100 buttons on my web page & i want to handle click event of each button. I have same coding on each button but the only difference is that, which button is calling the event handling routine. So i want to make one sub routine for handling event of all my buttons.
I can solve this by writing each button name in the handles clause like - Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ImgRCP_26.Click, ImgRCP_27.Click,. But it is so lengthy procedure. So that why i want to handle my button in the arraylist. How to do this?
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Apr 3, 2012
I have multiple user controls (the same one dynamically added to a form 4 times), and one class. I would like all of the user controls raise events in that one class. For example, if any of the user controls are clicked, I want it to send a string to the class to be processed and show a MsgBox "Control name was clicked"I am doing this as an exercise to reduce repeating the same code over and over directly in the control, and to avoid creating the class over and over to accompany each user control.
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Sep 4, 2009
I have a standard windows application called winap. I have a com component which acts as an api to the winap. I have a class in winap call classapi which has all the methods that the api calls and all works well. The problem is that one of the methods in my class api needs to get a handle on form elements in the main worker thread. Whenever I try to access an existing form I keep getting null because the for exists in the main worker thread and my api call is in a seperate thread.
[Code]...
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Dec 27, 2010
Is it possible to raise event in one class and handle the event in another class? If so, how?
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Mar 23, 2009
I wrote an application to handle a joystick with directinput. It works fine if it uses the handle of the main window but it doesnt happen the same if the handle is the one of the component that contains the joystick's operation.
I mean:
main form handle: 15
component handle (which is inside the window and the joystick needs the focus of this component to work): 25
It always work if the handle i initilizate the device is the main form (15).How can i use only the handle of the component?
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