VB.NET TUTORIALS - VB.Net - Exception Handling

VB.Net - Exception Handling

Exception Classes in .Net Framework

Exception Class	Description
System.IO.IOException	Handles I/O errors.
System.IndexOutOfRangeException	Handles errors generated when a method refers to an array index out of range.
System.ArrayTypeMismatchException	Handles errors generated when type is mismatched with the array type.
System.NullReferenceException	Handles errors generated from deferencing a null object.
System.DivideByZeroException	Handles errors generated from dividing a dividend with zero.
System.InvalidCastException	Handles errors generated during typecasting.
System.OutOfMemoryException	Handles errors generated from insufficient free memory.
System.StackOverflowException	Handles errors generated from stack overflow.

Syntax

Try
    [ tryStatements ]
    [ Exit Try ]
[ Catch [ exception [ As type ] ] [ When expression ]
    [ catchStatements ]
    [ Exit Try ] ]
[ Catch ... ]
[ Finally
    [ finallyStatements ] ]
End Try

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						Handling Exceptions

Module exceptionProg
   Sub division(ByVal num1 As Integer, ByVal num2 As Integer)
      Dim result As Integer
      Try
          result = num1 \ num2
      Catch e As DivideByZeroException
          Console.WriteLine("Exception caught: {0}", e)
      Finally
          Console.WriteLine("Result: {0}", result)
      End Try
   End Sub
   Sub Main()
      division(25, 0)
      Console.ReadKey()
  End Sub
End Module

						Creating User-Defined Exceptions

Module exceptionProg
   Public Class TempIsZeroException : Inherits ApplicationException
      Public Sub New(ByVal message As String)
          MyBase.New(message)
      End Sub
   End Class
   Public Class Temperature
      Dim temperature As Integer = 0
      Sub showTemp()
          If (temperature = 0) Then
              Throw (New TempIsZeroException("Zero Temperature found"))
          Else
              Console.WriteLine("Temperature: {0}", temperature)
          End If
      End Sub
   End Class
   Sub Main()
      Dim temp As Temperature = New Temperature()
      Try
          temp.showTemp()
      Catch e As TempIsZeroException
          Console.WriteLine("TempIsZeroException: {0}", e.Message)
      End Try
      Console.ReadKey()
   End Sub
End Module

						Throwing Objects

Throw [ expression ]

						
Module exceptionProg
   Sub Main()
      Try
          Throw New ApplicationException("A custom exception _
		  is being thrown here...")
      Catch e As Exception
          Console.WriteLine(e.Message)
      Finally
          Console.WriteLine("Now inside the Finally Block")
      End Try
      Console.ReadKey()
   End Sub
End Module