VB.Net/Language Basics/Throw

Any Exception generatesd will be caught in the Catch block that follows

Imports System
Public Class MainClass
   Shared Sub Main()
      Try
         Method1()
         " Output String representation of Exception, then output
         " values of properties InnerException, Message and StackTrace
      Catch exceptionParameter As Exception
         Console.WriteLine("exceptionParameter.ToString: " & _
            vbCrLf & "{0}" & vbCrLf, exceptionParameter.ToString())
         Console.WriteLine("exceptionParameter.Message: " & _
            vbCrLf & "{0}" & vbCrLf, exceptionParameter.Message)
         Console.WriteLine("exceptionParameter.StackTrace: " & _
            vbCrLf & "{0}" & vbCrLf, exceptionParameter.StackTrace)
         Console.WriteLine( _
            "exceptionParameter.InnerException: " & _
            vbCrLf & "{0}" & vbCrLf, _
            exceptionParameter.InnerException.ToString())
      End Try
   End Sub " Main
   Public Shared Sub Method1()
      Method2()
   End Sub
   Public Shared Sub Method2()
      Method3()
   End Sub
   Public Shared Sub Method3()
      " attempt to convert String to Integer
      Try
         Convert.ToInt32("Not an integer")
      Catch formatException As FormatException
         Throw New Exception("Exception occurred in Method3", _
            formatException)
      End Try
   End Sub
End Class

Catch and rethrow exceptions

Imports System
Imports System.Data
Imports System.IO
public class MainClass
   Shared Sub Main()
       Dim FileToRead As String = "test.txt"
       Dim TestFile As FileStream
       Dim Reader As New StreamReader(FileToRead)
       Do
           Dim I As Integer, S As String
           Dim Result As Integer
           Try
               S = Reader.ReadLine()
               I = CInt(S)
               Result = 100 \ I
               Console.WriteLine(Result)
           Catch DivByZero As System.DivideByZeroException
               Console.WriteLine("** Divide by zero **")
           Catch BadConversion As System.InvalidCastException
               Console.WriteLine("** " + S + " is not a number **")
               Throw New System.InvalidCastException("My own exception happened here", BadConversion)
           Catch OtherErrors As Exception
               Throw OtherErrors
           End Try
       Loop While Reader.Peek <> -1
   End Sub
End Class

Exception occurs and caught, then rethrown to caller

Imports System
Public Class MainClass
    
    Shared Sub Main(ByVal args As String())
      Console.WriteLine("Calling ThrowExceptionCatchRethrow")
      Try
         ThrowExceptionCatchRethrow()
      Catch
         Console.WriteLine("Caught exception from " & _
            "ThrowExceptionCatchRethrow in Main")
      End Try
    End Sub
   Public Shared Sub ThrowExceptionCatchRethrow()
      Try
         Console.WriteLine("In ThrowExceptionCatchRethrow")
         Throw New Exception("Exception in ThrowExceptionCatchRethrow")
      Catch exceptionParameter As Exception
         Console.WriteLine("Message: " & exceptionParameter.Message)
         Throw exceptionParameter
      Finally
         Console.WriteLine("Finally executed in ThrowException")
      End Try
      " any code placed here is never reached
      Console.WriteLine("End of ThrowExceptionCatchRethrow")
   End Sub 
End Class

Throw an Exception

Imports System
Imports System.Configuration
Imports System.Resources " Resource readers
Public Class MainClass
    
    Shared Sub Main()
       Throw New System.IO.FileLoadException()
    End Sub
End Class

Throw an Exception from a Function

Imports System
Imports System.Text 
Imports System.Text.RegularExpressions
Public Class MainClass
    Shared Sub Main(ByVal args As String())
             Console.WriteLine("Enter Run...")
             Func1( )
             Console.WriteLine("Exit Run...")
    End Sub
    
         Shared Public Sub Func1( )
             Console.WriteLine("Enter Func1...")
             Func2( )
             Console.WriteLine("Exit Func1...")
         End Sub "Func1
         Shared Public Sub Func2( )
             Console.WriteLine("Enter Func2...")
             Throw New System.Exception( )
             Console.WriteLine("Exit Func2...")
         End Sub "Func2
End Class

Throw Exception Without Catch

Imports System
Public Class MainClass
    
    Shared Sub Main(ByVal args As String())
      Try
         ThrowExceptionWithoutCatch()
      Catch
         Console.WriteLine("Caught exception from " & _
            "ThrowExceptionWithoutCatch in Main")
      End Try
    End Sub
    Shared Public Sub ThrowExceptionWithoutCatch()
      Try
         Console.WriteLine("In ThrowExceptionWithoutCatch")
         Throw New Exception( _
            "Exception in ThrowExceptionWithoutCatch")
      Finally
         Console.WriteLine("Finally executed in " & _
            "ThrowExceptionWithoutCatch")
      End Try
      " unreachable code; logic error 
      Console.WriteLine("End")
   End Sub 
    
End Class

Throws exception and catches it locally

Imports System
Public Class MainClass
    
    Shared Sub Main(ByVal args As String())
   
      " Try block throws exception
      Try
         Console.WriteLine("In Throw Exception With Catch")
         Throw New Exception("Exception in Throw Exception With Catch")
         " catch exception thrown in Try block
      Catch exceptionParameter As Exception
         Console.WriteLine("Message: " & exceptionParameter.Message)
         " Finally executes because corresponding Try executed
      Finally
         Console.WriteLine( _
            "Finally executed in Throw Exception With Catch")
      End Try
      Console.WriteLine("End")
    End Sub
End Class