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Friday, 2 November 2012

On Error GoTo statements in VB.NET


  On Error GoTo statements is an example of Vb.Net's Unstructured Exception Handling . VB.NET has two types of Exception handling . Structured Error Handling and Unstructured Error handling . VB.NET using Try..Catch statement for Structured Error handling and On Error GoTo statement is using for Unstructured Error handling.
Error GoTo redirect the flow of the program in a given location.
On Error Resume Next - whenever an error occurred in runtime , skip the statement and continue execution on following statements.
Take a look at the following program
VB.NET Source Code
  Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles Button1.Click
        Dim result As Integer
        Dim num As Integer
        num = 100
        result = num / 0
        MsgBox("here")
    End Sub
End Class

when u execute this program you will get error message like " Arithmetic operation resulted in an overflow "
See the program we put an On Error GoTo statement

Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles Button1.Click
        On Error GoTo nextstep
        Dim result As Integer
        Dim num As Integer
        num = 100
        result = num / 0
nextstep:
        MsgBox("Control Here")
    End Sub
End Class

When you execute the program you will get the message box "Control Here" . Because the On Error statement redirect the exception to the Label statement.        

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