Demonstrating a user-defined exception class : Custom Exception « Development « VB.Net Tutorial

1. VB.Net Tutorial
2. Development
3. Custom Exception

Public Class Tester
    Public Shared Sub Main
    
      Try
         Console.WriteLine(SquareRoot(123.123))
         Console.WriteLine(SquareRoot(-123.123))

      Catch formatException As FormatException
         Console.WriteLine(formatException.Message)

      Catch negativeNumberException As _
         NegativeNumberException
         Console.WriteLine(negativeNumberException.Message)
      End Try
    End Sub
   Public Shared Function SquareRoot(ByVal operand As Double) As Double

      If operand < 0 Then
         Throw New NegativeNumberException( _
            "Square root of negative number not permitted")
      End If

      Return Math.Sqrt(operand)
   End Function ' cmdSquareRoot

End Class


Public Class NegativeNumberException
   Inherits ApplicationException

   Public Sub New()
      MyBase.New("Illegal operation for a negative number")
   End Sub ' New

   Public Sub New(ByVal messageValue As String)
      MyBase.New(messageValue)
   End Sub ' New

   Public Sub New(ByVal messageValue As String, _
      ByVal inner As Exception)
      MyBase.New(messageValue, inner)
   End Sub

End Class

11.0960803890383
Square root of negative number not permitted