Custom Error vs Custom Exception

I am in the process of updating some vb6 code to vb.net. The error handling in this old code uses On Error GoTo or On Error Resume Next with error handles at the end of each method.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

Now that I am updating this code to vb.net I am changing all error handling to try - catch statements. I can either wrap the Public Sub Main function in a try - catch statement and catch all errors at the top level or swap out the above code for the following:

Public Function Init() As Boolean
    Try
        Init = True
    catch e As exception
        Init = false
    End Try
End Function

My Problem comes when, in the old code, a custom error is set (Error 9999) if certain If statements are not met. In the Error handles at the end of the function, it checks if the error is not 9999. If it is not then it handles it appropriately. Using the first example:

Public Function Init() As Boolean
    On Error GoTo Err_Init
    Dim a As Integer
    If (a <> 10)
        Init = True
    Else
        Error 9999
    End If
Exit_Init: 
    Exit Function 
Err_Init:
    If (Err.number() <> 9999)
        Init = False
    End If
    Resume Exit_Init
End Function

So my question is, how can I use try-catch statements to replicate this error 9999, as throughout my code it will not always be the same exception that is thrown, hence why just throwing a custom error 9999 could be used across the board and used to mark the errors that could be ignored, and then you can just catch the important errors. Is there a way to Throw New Exception(Id = 9999), sort of thing?

Solution

You should create a custom exception and treat separetly in your catch. Here's some example on how to create your custom exception: https://msdn.microsoft.com/en-us/library/87cdya3t(v=vs.110).aspx

And then code something this way:

Public Function Init() As Boolean
     Try
        If (a = 10) Then
          Throw New YourCustomException()
        End If
     Catch yourEx As YourCustomException
        'Do whatever you want to do when the code throws your custom exception            
     Catch generalException As Exception
        Return False
     End Try

     Return True
End Function