try catch block in vb.net

Exceptions are the occurrence of some condition that changes the normal flow of execution (simply when you get some errors or your program is crashed for that you can show he errors by using try... catch block). For ex: your program is run out of memory, file does not exist in the given path, network connections are dropped etc. More specifically for better understanding, we can say it as Runtime Errors.

In .NET languages, Structured Exceptions handling is a fundamental part of Common Language Runtime. It has a number of advantages over the On Error statements provided in previous versions of Visual Basic. All exceptions in the Common Language Runtime are derived from a single base class, also you can create your own custom Exception classes. You can create an Exception class that inherits from Exception class.

You can handle Exceptions using Try..Catch statement .

  Try

                code

                exit from Try

  Catch [Exception [As Type]]

                code - if the exception occurred this code will execute

                exit from Catch

Finally

The code in the finally block will execute even if there is no Exceptions. That means if you write a finally block , the code should execute after the execution of try block or catch block.

  Try

                code

                exit from Try

  Catch [Exception [As Type]]

                code - if the exception occurred this code will execute

                exit Catch

  Finally

                code - this code should execute , if exception occurred or not

From the following VB.NET code , you can understand how to use try..catch statements. Here we are going to divide a number by zero .

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Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, _

    ByVal e As System.EventArgs) Handles Button1.Click

        Try

            Dim i As Integer

            Dim resultValue As Integer

            i = 100

            resultValue = i / 0

            MsgBox("The result is " & resultValue)

        Catch ex As Exception

            MsgBox("Exception catch here ..")

        Finally

            MsgBox("Finally block executed ")

        End Try

    End Sub

End Class

When you execute this program you will "Exception catch here .." first and then "Finally block executed " . That is when you execute this code , an exception happen and it will go to catch block and then it will go to finally block.