While the title might be confusing, I hope this will explain it better.
So, I want to make an VB.Net webbrowser with a GeckoWebBrowser control.
The issue I am facing is that Gecko keeps opening error dialogs even tho I am catching the Error in my code. I just want to disable those dialogs and load an simple html site instead.
Code (Where wbMain is the GeckoWebBrowser control):
Function navigate(ByVal address As String)
Try
wbMain.Navigate(address)
Catch ex As Exception
wbMain.LoadHtml("<h1>An error has occurred!</h1><p>Description: " & ex.Message & "</p>")
End Try
End Function
Gecko keeps doing those errors:
error (I can't post images yet)
But I just want it to display the html page instead of the dialog.
I apologize if I wasn't clear enough or have broken english
I suppose these are the browser alerts, so you need to create your own service which catches these messages.
Create a class which implements the nsIPromptService2 and nsIPrompt prompt interface. In VB syntax is like that I suppose:
class FilteredPromptService Implements nsIPromptService2, nsIPrompt
And then override all the methods required by these interfaces with your own custom logic.
Related
Need help with some VB.net coding (NOT C or c++)
So far I'm using this code to catch errors for specific line(s) of codes:
Try
bla bla bla
Catch ex As Exception
msbox("Error: " & ex.message)
End Try
But sometimes the application stops due to an error where I don't have a catch; how do I on occasions like this call upon a specific Sub (catch the error) for ANY OTHER error in the ENTIRE application where the Sub will display the error message (where I also plan on sending my self an e-mail in that sub to notify me application has stopped)?
I'm not sure if it will conflict with all current Try/Catch commands in my application, but I would prefer to only catch the error on code that currently is not within a Catch handler.
Thank you so much!
This functionality is built into the VB application framework, which is enabled by default in WinForms applications. Open the Application page of the project properties, click the View Application Events button and add a handler for the UnhandledException event using the navigation bar at the top of the code window. Done!
The VB application framework hides some of the complexity of applications that you must implement yourself in C#. It includes a Startup event that you can handle instead of adding code to a Main method, a StartupNextInstance event to support single-instance apps with commandline arguments, multi-threaded splash screen functionality and more.
Regarding your emailing idea, just sure to add in a privacy notice before auto-emailing yourself anything in your apps; this can be a big bone of contention to users, & if an astute one catches it silently phoning home your rep is down the drain.
As for a global error handler, have a look here:
https://www.dotnetcurry.com/patterns-practices/1364/error-handling-dotnet-projects
Is there a simple way to catch all exceptions in your VB.NET applications? I'm interested in making it so that instead of my users seeing a runtime error, they just are told that an error occurred and to contact tech support, then the relevant error information is logged so our support team can look at it afterwards.
You can use the OnUnhandledException application event to catch (almost) every exception that wasn't handled by the code.
On the Project Properties window (double-click project file on the solution explorer or Project Menu -> [Project name] properties), the Application page has a "View Application Events" button that creates a new file in your project.
In that file there are some events that are fired at application level; one of those is the UnhandledException. Whatever you put there will be executed instead of the classic JIT dialog. The UnhandledExceptionEventArgs object has an Exception property with the unhandled exception object, and a ExitApplication property that decides if the application should exit or continue executing.
Namespace My
' The following events are available for MyApplication:
'
' Startup: Raised when the application starts, before the startup form is created.
' Shutdown: Raised after all application forms are closed. This event is not raised if the application terminates abnormally.
' UnhandledException: Raised if the application encounters an unhandled exception.
' StartupNextInstance: Raised when launching a single-instance application and the application is already active.
' NetworkAvailabilityChanged: Raised when the network connection is connected or disconnected.
Partial Friend Class MyApplication
Private Sub MyApplication_UnhandledException(sender As Object, e As Microsoft.VisualBasic.ApplicationServices.UnhandledExceptionEventArgs) Handles Me.UnhandledException
MessageBox.Show(e.Exception.ToString) '<-- the exception object
e.ExitApplication = True '<-- True if you want the application to close; false to continue - if it can
End Sub
End Class
End Namespace
Note that there are still some "über-exceptions" that can't be caught even with this method (out of memory for example), but this way you can log what exceptions are not being correctly handled on your code, or what scenarios are actualy happening that weren't considered at the beggining.
More info here
As a side note: don't rely too much on this event. This has to be for extremely exceptional cases, as what is caught here should be treated ASAP in the corresponding class/module/method. This is a helpful tool for debugging and test cases but having too much exceptions being handled by this event would be a sign of something wrong in your code.
It depends on what environment your application is running in. If you are using WPF or WinForms, you would launch your application using a main method instead of directly launching a form or page. Your main method should then wrap the calls to instantiate the UI in a try catch block.
So, for a WinForms Application, you could do something like this:
Sub Main
Try
Dim MainUI As New Form1
MainUI.Show()
Application.Run
Catch ex As Exception
'Do that fancy exception processing
End Try
End Sub
You can do something similar with WPF. But, WPF also supports an event model where you are notified of exceptions, very similar to the one that ASP.Net uses.
You will never be able to catch the StackOverflowException.
All the others for sure yes. I'm not familiar with VB, but it is easy to achieve in C#. For VB, I think the generic exeption handler could be
Try
...
Catch e As Exception
...
End Try
Of course this has to wrap all your code. You can find more for examples here.
If you have forms application, it is not practical to have the handler around Application.Run() as the only event handler. Keep it there, but add also two others:
When inside the form, and exception occurs, you want to keep execution in that context – keep the form open etc. For this purpose, use ThreadExceptionEventHandler.
And also, for case when application is irrepairably crashing on some problem, add handler to Dispatcher.UnhandledException event. It is last thing executed before the application ends. You can log the exception to disk for later investigation etc. Very useful.
Let's see some good resource how they are applied.
I'm creating an add-in for Solidworks EPDM (example from API help). This is a class library (.dll) project which is added to EPDM and allows some custom functions to be added to the program.
I want to add logging for unhandled errors so that when an exception is caused by my add-in (as opposed to by the Solidworks EPDM program itself) I can be notified of it and try to fix it.
I'm quite new to all of this (and by all of this I mean VB.NET as a language, programming anything other than macros in VBA, structured exception handling, error logging, etc) and I'm trying to follow MSDN How To: Log Exceptions in Visual Basic but the instructions for logging unhanlded exceptions don't seem applicable to class library projects.
Specifically, I don't know how to get past step 3:
To log an unhandled exception
1. Have a project selected in Solution Explorer. On the Project menu, choose Properties.
2. Click the Application tab.
3. Click the View Application Events button to open the Code Editor.
This opens the ApplicationEvents.vb file.
The View Application Events button is greyed out for class library projects.
So, is there another way to add logging for unhandled exceptions in class library projects? Or, another way to access the ApplicationEvents.vb file for class library objects? I've tried searching for either, and have yet to find a solution that would allow me to log unhandled exceptions.
This is a very basic example but wrap your code with Try/Catch in the only two interface methods (host "callbacks") that IEdmAddIn5 defines and which your add-in class must implement.
Public Sub GetAddInInfo(ByRef poInfo As EdmAddInInfo, ByVal poVault As IEdmVault5, ByVal poCmdMgr As IEdmCmdMgr5) Implements IEdmAddIn5.GetAddInInfo
Try
...
Catch ex As Exception
' Handle exception...
End Try
End Sub
Public Sub OnCmd(ByRef poCmd As EdmCmd, ByRef ppoData As System.Array) Implements IEdmAddIn5.OnCmd
Try
...
Catch ex As Exception
' Handle exception...
End Try
End Sub
I would ordinarily agree with #Hans Passant about re-throwing the exception but I generally have found that to be problematic with an EPDM add-ins as it can cause the COM host to crash.
I'm trying to make a Runescape Client in Visual Basic, but when I run http://www.runescape.com/game in a web browser it tells me to install java
It brings up an error saying:
*An error has occurred in the script on this page.
line: 48
Char: 325
Error: Expected ')'
code: 0
URL: http://www.runescape.com/game
Do you want to continue running the scripts on this page?
(Yes/No)*
I need a way to run Runescape inside a visual basic Application.
Is there any way to add java to the web browser?
Any help would be appreciated :)
This is due to a JS error, the easiest fix is to input in the Form load,
WebBrowser1.ScriptErrorsSuppressed = True
Hopefully that works?
It looks like you are getting this error, which is a JavaScript error on the page, not a Java error on your machine.
To resolve, you need to clear the "Display a notification about every script error" check box in the Advanced section of the Internet Options menu. Here's a lengthy article on Microsoft Support describing how to access and change the Internet Options via VB.Net.
The relevant code from that page to access the Internet Options:
Public Sub InternetOptions()
Dim cmdt As IOleCommandTarget
Dim o As Object
Try
cmdt = CType(GetDocument(), IOleCommandTarget)
cmdt.Exec(cmdGUID, Convert.ToUInt32(MiscCommandTarget.Options), _
Convert.ToUInt32(SHDocVw.OLECMDEXECOPT.OLECMDEXECOPT_DODEFAULT), o, o)
Catch
' NOTE: Due to the way this CMDID is handled inside of Internet Explorer,
' this Catch block will always fire, even though the dialog
' and its operations completed successfully. Suppressing this
' error will cause no harm to your host.
End Try
End Sub
just set the webbrowser ScriptErrorsSuppressed property to true and thats all
I am new to multi-threading in VB.NET and have come across a problem whereby I am wanting to append text to a text box on a form from a service thread running in the background.
The application I am developing is a client/server listener, I have been able to get the client and server PC's to talk with each other (confirmed through MsgBox), however I am now struggling to get the service thread on the server to append the text to the textbox, nothing vissible occurs.
I have a form named testDebug which calls a class (RemoteSupport), this class does all the handshake tasks and updates the textbox with the connection data.
Can anyone identify where I am going wrong and point me in the right direction?
The following is the code I have:
The form has a textbox named txtOutput, the following is from the remoteSupport class
Dim outMessage As String = (encoder.GetString(message, 0, bytesRead))
MsgBox(outMessage, MsgBoxStyle.Information, "MEssage Received")
If outMessage IsNot Nothing Then
If testDebug.InvokeRequired Then
' have the UI thread call this method for us
testDebug.Invoke(New UpdateUIDelegate(AddressOf HandleClientComm), New Object() {outMessage}) '
Else
testDebug.txtOutput.AppendText(outMessage)
End If
'RaiseEvent MessageReceived(outMessage) // a previous attempt to use custom events
End If
I am not sure if the invoke method is the ideal solution or if custom events are, I have spent some time on trying to get custom events to work, but these didnt work either.
// In the RemoteSupport class
Public Delegate Sub MessageReceivedHandler(ByVal message As String)
Public Shared Event MessageReceived As MessageReceivedHandler
// Located throughout the RemoteSupport class where debug information is required.
RaiseEvent MessageReceived(outMessage)
// Located in the code-behind of the form
Private Sub Message_Received(ByVal message As String)
testDebugOutput(message) // this is a function I have created
// to append the text to the text box
End Sub
The code supplied has been cut down so if there is anything else that you want to see or any questions please let me know.
Thanks for your assistance.
EDIT: I have uploaded the two VB files (form and class) to my site, I would appreciate it if someone could have a look at it to help me with identifying the problem with the UI not updating.
I have tried a few other things but nothing seems to be updating the UI once the worker thread has started.
Form: mulholland.it/testDebug.vb.txt
Class: mulholland.it/remoteSupport.vb.txt
Thanks for your assistance.
Matt
I have a form named testDebug...
If testDebug.InvokeRequired Then
This is a classic trap in VB.NET programming. Set a breakpoint on the If statement. Notice how it returns False, even though you know that the code is running on another thread?
InvokeRequired is an instance property of a Form. But testDebug is a class name, not a reference to an instance of a form of type testDebug. That this is possible in VB.NET has gotten a lot of VB.NET programmers in deep trouble. It is an anachronism carried over from VB6. It completely falls apart and blows up in your face when you do this in a thread. You'll get a new instance of the form, instead of the one that the user is looking at. One that isn't visible because its Show() was never called. And otherwise dead as a doornail since the thread isn't running a message loop.
I answered this question several times already, with the recommended fix. I'll just refer you to them rather than rehashing it here:
Form is not updating, after custom class event is fired
Accessing controls between forms
The Delegate method is likely the way you want to go, but I don't see the declaration of the UpdateUIDelegate anywhere
I believe your code should look something like this (assuming you have a reference to the testdebug form local to your remotesupport class
Dim outMessage As String = (encoder.GetString(message, 0, bytesRead))
MsgBox(outMessage, MsgBoxStyle.Information, "MEssage Received")
If outMessage IsNot Nothing Then
If testDebug.InvokeRequired Then
' have the UI thread call this method for us
testDebug.Invoke(New MessageReceivedHandler(AddressOf Testdebug.Message_Received), New Object() {outMessage})
Else
testDebug.txtOutput.AppendText(outMessage)
End If
end if