Custom Exception Handling in VB.NET
This article gives you a idea about exception handling in Visual Basic.Net and also how you can create your own custom exceptions.
Exception
Exceptions are the occurrence of some condition that changes the normal flow of
execution .
For
example:
Your
program run out of memory , file does not exist in the given path , network
connections are dropped etc. More specifically for better understanding , we can
say it as Runtime Errors .
The
Concept
The whole idea of having customized Exception Handling is centered around the
fact that there needs to be a generic approach of catching and throwing
Exceptions.
For implementing custom Exception Handling we need to derive the class
CustomException from the system base class ApplicationException. In general, for
customizing Exception Handling the following components are necessary:
1. A custom exception class which would host the exception thrown and can be
thrown as a new exception.
2. A message class that would host all user - friendly Application messages that
need to be displayed.
Creating
Custom Exception
VB.NET define your own custom
exceptions to identify the occurrence of unexpected events in your
code.exceptions are implemented in VB.Net as classes and objects.
-
Create a exception kind of class and inherit
it from Exception class.
-
Override the Message property and
ToString() method.
For example:
Module
Module1
Class
NotEnoughBalanceException
Inherits
Exception
Public
Overrides ReadOnly
Property Message()
As String
Get
Return "Sorry! Not Engouh Balance"
End
Get
End
Property
End
Class
Class
Customer
Private
name As String
Private
balance As Integer
Public
Sub New(ByVal
name As String,
ByVal opamt As
Integer)
Me.name
= name
Me.balance
= opamt
End
Sub
Public
Sub Deposit(ByVal
amount As Integer)
balance += amount
End
Sub
Public
Sub Withdraw(ByVal
amount As Integer)
If
amount > balance Then
Throw New
NotEnoughBalanceException()
End
If
balance -= amount
End
Sub
Public
Sub ShowBalance()
Console.WriteLine("Balance
of {0} is {1}", name, balance)
End
Sub
End
Class
Class
ExpTest
Public
Shared Sub
Main()
Dim
c As New
Customer("Amit",
5000)
Try
c.Deposit(4000)
c.ShowBalance()
c.Withdraw(20000)
c.ShowBalance()
Catch
ex As
NotEnoughBalanceException
Console.WriteLine(ex.Message)
End
Try
End
Sub
End
Class
End
Module
OUTPUT:

Conclusion:
Hope this article would have helped you in understanding custom exception
handling in VB.NET.