vb.net - error handling on main method or every method - vb.net

Question

I have a program that is interacting with emails. I am upgrading it from vb6 to vb.net. There was extensive error handling in the program before ,using On Error commands, to ensure that it never broke, just ignored and logged the errors. In most functions there is this On Error code, where it handles an error in the function by returning a default value and exiting the function. For Example:
Public Function Init() As Boolean
On Error GoTo Err_Init
Init = True
Exit_Init:
Exit Function
Err_Init:
Init = False
Resume Exit_Init
End Function
I want to change all error handling to Try - Catch blocks. My initial thought when I was upgrading the vb6 code was to replace all error handling with a simple Try - Catch around the Sub Main entry point, as below:
Public Sub Main()
Try
Init()
catch
'do stuff
end try
End Sub
public function Init() As boolean
init = true
end function
as any errors in the program would be caught in this way and I could handle them all in one Try - Catch.
However I then realised that, that would not make the function above return a value of False when an error occurred. If I still want this functionality do I have to wrap everything in Try blocks?

Answer 1

Since your concern is that you do not want the application to crash or break, Yes you can use Try cache block for that concern.
However, If you are talking about error handling in the whole application, then I would suggest that you think of a way to refactor the whole code.
Remove all the "On Error" statements and apply some new logic to handle the errors.
That logic could vary (Only logging, Retrying strategy Design pattern, etc) Think of all the expected errors and handle them accordingly.

Answer 2

If you need to do something special for errors in a particular function, then the function should have its own Try/Catch block to implement that behavior. For example:
Public Function Init() As Boolean
Try
'Presumably some other code goes here
Return True
Catch ex As Exception
Return False
End Try
End Function

Answer 3

Get rid of all the on Error steps and do the error handling globally
In the main_load put the three block below
' Get your application's application domain for error handling.
Dim currentDomain As AppDomain = AppDomain.CurrentDomain
' Define a handler for unhandled exceptions.
AddHandler currentDomain.UnhandledException, AddressOf MYExnHandler
' Define a handler for unhandled exceptions for threads behind forms.
AddHandler Application.ThreadException, AddressOf MYThreadHandler
and then add the two sub routines shown below
Private Sub MYExnHandler(ByVal sender As Object,
ByVal e As UnhandledExceptionEventArgs)
Dim EX As Exception
EX = e.ExceptionObject
If EX.StackTrace.Contains("SOMETHING") Then
My.Computer.FileSystem.WriteAllText(LogToWrite, "Error SOMETHING caught:" & EX.StackTrace & vbCrLf, True, System.Text.Encoding.Default)
MsgBox("error caught. Contact **XXX** for assistance!" & vbCrLf & vbCrLf & "Error: " & vbCrLf & EX.StackTrace,, "Fatal Error")
End If
End Sub
Private Sub MYThreadHandler(ByVal sender As Object,
ByVal e As Threading.ThreadExceptionEventArgs)
If e.Exception.StackTrace.Contains("SOMETHING") Then
My.Computer.FileSystem.WriteAllText(LogToWrite, "Error SOETHING caught:" & e.Exception.StackTrace & vbCrLf, True, System.Text.Encoding.Default)
MsgBox("Error caught. Contact **xxx** for assistance!" & vbCrLf & vbCrLf & "Error: " & vbCrLf & e.Exception.StackTrace,, "Fatal Error")
End If
End Sub
You can just check the content of the errors and respond accordingly to every single error with a Case Array..