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==Basics of Visual Basic exception handling==

<source lang="vbnet">Public Class Tester
Public Shared Sub Main

Try
Dim numerator As Integer = Convert.ToInt32("123")
Dim denominator As Integer = Convert.ToInt32("321")
Dim result As Integer = numerator \ denominator
Console.WriteLine(result)
Catch formattingException As FormatException
Console.WriteLine("You must enter two integers")
Catch dividingException As DivideByZeroException
Console.WriteLine(dividingException.Message)
End Try
End Sub
End Class</source>
<pre class=codeResult>0</pre>

==Catch Exception in a function==

<source lang="vbnet">Module Module1
Sub Main()
Try
AddNumbers(1, 2)
Catch Except As Exception
Console.WriteLine("Call generated error: " & Except.Message)
End Try
End Sub
Function AddNumbers(ByVal A As Integer, ByVal B As Integer) As Integer
Try
Throw New ArithmeticException()
Catch Except As Exception
Console.WriteLine(Except.Message)
End Try
End Function
End Module</source>
<pre class=codeResult>Overflow or underflow in the arithmetic operation.</pre>

==Convert Exception to String==

<source lang="vbnet">Module Module1
Sub Main()
Dim A, B, C As Integer
A = 3
B = 0
Try
C = A Mod B
Catch Except As Exception
Console.WriteLine(Except.ToString())
End Try

End Sub
End Module</source>
<pre class=codeResult>System.DivideByZeroException: Attempted to divide by zero.
at Module1.Main()</pre>

==Display Exception Trace==

<source lang="vbnet">Module Module1
Sub Main()
Try
Console.WriteLine("Result: ", First())
Catch Except As Exception
Console.WriteLine(Except.StackTrace)
End Try
End Sub
Private Function First() As Integer
First = Second()
End Function
Private Function Second() As Integer
Second = Third()
End Function
Private Function Third() As Integer
Dim A As Integer = 0
Third = 100 Mod A
End Function
End Module</source>
<pre class=codeResult>at Module1.Main()</pre>

==Exception fields==

<source lang="vbnet">Imports System.IO
Module Module1
Sub Main()
Dim SourceFile As StreamReader
Try
SourceFile = New StreamReader("FilenameISBad.XXX")
Catch Except As Exception
Console.WriteLine(Except.Message)
Console.WriteLine(Except.Source)
Console.WriteLine(Except.StackTrace)
Console.WriteLine(Except.TargetSite.Name)
End Try
End Sub
End Module</source>

==Get Message from Exception==

<source lang="vbnet">Module Module1
Sub Main()
Dim A, B, C As Integer
A = 3
B = 0
Try
C = A Mod B
Catch Except As Exception
Console.WriteLine(Except.Message())
End Try
End Sub
End Module</source>
<pre class=codeResult>Attempted to divide by zero.</pre>

==Serializable Exception Inheriting NullReferenceException==

<source lang="vbnet">Imports System
Imports System.Runtime.Serialization
<Serializable()> Public Class NodeNotFoundException : Inherits NullReferenceException
Dim st As String()
"Constructors
Public Sub New()
MyBase.New("No such node found in your collection.")
End Sub
Public Sub New(ByVal message As String)
MyBase.New(message)
End Sub
Public Sub New(ByVal message As String, ByVal inner As Exception)
MyBase.New(message, inner)
End Sub
End Class</source>

==Set Exception HelpLink==

<source lang="vbnet">Option Strict On
Imports System
Class Tester
Public Shared Function DoDivide(ByVal a As Double, ByVal b As Double) As Double
If b = 0 Then
Dim e As New System.DivideByZeroException( )
e.HelpLink = "http://www.vbex.ru"
Throw e
End If
If a = 0 Then
Throw New System.ArithmeticException( )
End If
Return a / b
End Function "DoDivide
Shared Sub Main( )
Try
Dim a As Double = 5
Dim b As Double = 0
Console.WriteLine("{0} / {1} = {2}", a, b, DoDivide(a, b))
Catch e As System.DivideByZeroException
Console.WriteLine("DivideByZeroException! Msg: {0}", e.Message)
Console.WriteLine("Helplink: {0}", e.HelpLink)
Console.WriteLine("Stack trace: {0}", e.StackTrace)
Catch
Console.WriteLine("Unknown exception caught!")
Finally
Console.WriteLine("Close file here.")
End Try
End Sub "Main
End Class "Tester</source>
<pre class=codeResult>DivideByZeroException! Msg: Attempted to divide by zero.
Helplink: http://www.vbex.ru
Stack trace: at Tester.DoDivide(Double a, Double b)
at Tester.Main()
Close file here.</pre>

==Throw Exception out of a Method==

<source lang="vbnet">Option Strict On
Imports System
Class Tester
Shared Sub Main( )
Console.WriteLine("Enter Main...")
Console.WriteLine("Enter Run...")
Func1( )
Console.WriteLine("Exit Run...")
Console.WriteLine("Exit Main...")
End Sub
Public Shared Sub Func1( )
Console.WriteLine("Enter Func1...")
Func2( )
Console.WriteLine("Exit Func1...")
End Sub

Public Shared Sub Func2( )
Console.WriteLine("Enter Func2...")
Throw New System.Exception( )
Console.WriteLine("Exit Func2...")
End Sub
End Class</source>
<pre class=codeResult>Enter Main...
Enter Run...
Enter Func1...
Enter Func2...
Unhandled Exception: System.Exception: Exception of type "System.Exception" was thrown.
at Tester.Func2()
at Tester.Main()</pre>

==Use properties Message, StackTrace and InnerException==

<source lang="vbnet">Class Tester
Shared Sub Main()
Try
Method1()
Catch exceptionParameter As Exception
Console.WriteLine(exceptionParameter.ToString())
Console.WriteLine(exceptionParameter.Message)
Console.WriteLine(exceptionParameter.StackTrace)
Console.WriteLine(exceptionParameter.InnerException.ToString())
End Try
End Sub
Public Shared Sub Method1()
Method2()
End Sub
Public Shared Sub Method2()
Method3()
End Sub
Public Shared Sub Method3()
Try
Convert.ToInt32("Not an integer")
Catch formatException As FormatException
Throw New Exception("Exception occurred in Method3", _
formatException)
End Try
End Sub
End Class</source>
<pre class=codeResult>System.Exception: Exception occurred in Method3 ---> System.FormatException: Input string was not in
a correct format.
at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFor
matInfo info, Boolean parseDecimal)
at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
at Tester.Method3()
--- End of inner exception stack trace ---
at Tester.Method3()
at Tester.Main()
Exception occurred in Method3
at Tester.Method3()
at Tester.Main()
System.FormatException: Input string was not in a correct format.
at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFor
matInfo info, Boolean parseDecimal)
at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
at Tester.Method3()</pre>

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