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How can I create a custom exception class in vb.net

Posted on 2007-11-29
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Last Modified: 2012-08-14
I am using vb.net 2003 to create a custom exception handling class.  The code that I am currently using works fine but I will need to use this exception handling pages containing data connections, queries, etc. and would like to just access a custom class.   Here is a short version of the code that is working and the code snippet attached is what I have in the class so far.  The line ex.message.tostring is not working.  Any help or direction on how to accomplish this would be appreciated.  Thank-you very much.
        Try
        Catch ex As Exception
            'WORKING CODE
            'Dim file As New System.IO.StreamWriter(Server.MapPath("..\ErrorLog.txt"), True)
            'file.WriteLine(FormatDateTime(Date.Now, DateFormat.GeneralDate))
            'file.WriteLine(ex.Message.ToString())
            'file.WriteLine(ex.Source.ToString())
            'file.WriteLine(ex.StackTrace.ToString())
            'file.Close()
            'Response.Redirect("http://localhost/NetTestDocs/ErrorsRedirectPage.aspx")
            'END OF CODE
        Finally
            conn.Close()
            conn.Dispose()
        End Try
    End Sub
Public Class ErrorsClass
    Public ex As Exception
    Sub writererror()
        'Dim file As New System.IO.StreamWriter(Server.MapPath("..\ErrorLog.txt"), True)
        Dim file As New System.IO.StreamWriter(HttpContext.Current.Server.MapPath("..\ErrorLog.txt"), True)
        file.WriteLine(FormatDateTime(Date.Now, DateFormat.GeneralDate))
        'file.WriteLine(ex.Message.ToString())
        file.Close()
    End Sub
 
End Class

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Question by:lnshop
  • 3
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6 Comments
 
LVL 25

Expert Comment

by:InteractiveMind
ID: 20379240
In the catch block, re-throw your exception, but to your custom class.

An example here:
http://www.vbdotnetheaven.com/UploadFile/susanabraham/CustomExceptionHandlingvb11122005021337AM/CustomExceptionHandlingvb.aspx?ArticleID=4ce8bdfe-1a63-44da-a4a3-f8e796d63302


When you say that ex.Message.ToString() is "not working", do you mean that it's returning an empty string?

If you replace these two lines:

         'file.WriteLine(ex.Message.ToString())
         'file.WriteLine(ex.Source.ToString())

with

         'file.WriteLine(ex.ToString())

does it include the expected message? (Wishful thinking here)
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LVL 44

Expert Comment

by:Arthur_Wood
ID: 20381315
you can also create your own Exception, by crearing a class the inherits from Exception:


     
Public Class MyException Inherits Exception
   Private _exceptionMessage as String
   Public ReadOnly Property ExceptionMessage() as String
      Property Get
       Return _exceptionMessage 
      End Get
   End property
   Public Sub New(ByVal Message as String)
      MyBase.New("Custom Error")
      _exceptionMessage = Message
   End Sub
 
End Class
 
 
Then you can use it like this:
 
     Try
        If someCondition then
            Throw New MyException("Something dreadful has happened")
        End if
     Catch ex as MyException
          MessageBox.Show(ex.ExceptionMessage, vbOkOnly
     Finally
     End try

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Author Comment

by:lnshop
ID: 20385195
Thank-you so much for your help.  I have the error message working now but I am having a problem adding the error source.  Attached is the class code.  How can I add the error source to the text file.   I have tried adding source as a property and have tried adding innerException and can't get this to work. If you could help me with adding the exception source, I would appreciate it very much.

'CODE IN VB CODE BEHIND
        Catch ex As Exception
            'REFERENCE TO ERRORS CLASS
            Dim myerror As ErrorsClass
            myerror = New ErrorsClass(ex.Message)
            myerror.writererror()

'ERRORS CLASS
Imports System.Exception
Public Class ErrorsClass
    Inherits Exception
    Private _exceptionMessage As String
    Public ReadOnly Property exceptionMessage() As String
        Get
            Return _exceptionMessage
        End Get
    End Property
    Public Sub writererror()
        Dim file As New System.IO.StreamWriter(HttpContext.Current.Server.MapPath("..\ErrorLog.txt"), True)
        file.WriteLine(FormatDateTime(Date.Now, DateFormat.GeneralDate))
        file.WriteLine(Message.ToString())
        file.Close()
    End Sub
End Class

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LVL 44

Accepted Solution

by:
Arthur_Wood earned 1000 total points
ID: 20386916
you need a way to create the message text.  Try this:


Imports System.Exception
Public Class ErrorsClass
    Inherits Exception
    Private _exceptionMessage As String
    Private _errorSource as String
    Public ReadOnly Property exceptionMessage() As String
        Get
            Return _exceptionMessage
        End Get
    End Property
 
    Public Sub New(byVal Message as String, byVal Source as string)
        _exceptionMessage = Message
        _errorSource = Source
    End Sub
    Public Sub writererror()
        Dim file As New System.IO.StreamWriter(HttpContext.Current.Server.MapPath("..\ErrorLog.txt"), True)
        file.WriteLine("Error occurred at: " & FormatDateTime(Date.Now, DateFormat.GeneralDate))
        file.WriteLine("Source = " & _errorSource)
        file.WriteLine("Error Message = " & _exceptionMessage)
        file.Close()
    End Sub
End Class
 
 
Then when you want to Throw the Exception:
    Try
       Code that creates the original exception
       .
       .
    Catch ex as Exception
       Throw New ErrorClass(ex.Message, "Procedure Name where the Error occurred")
    End Try
 
AW

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Author Comment

by:lnshop
ID: 20396830
Thank-you very much.  That works great.  I have the source and stack trace being written to the error log now.
0
 
LVL 44

Expert Comment

by:Arthur_Wood
ID: 20398683
Glad to be of assistance

AW
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