Catching an Exception using ASP.NET 2.0 and VB .NET

This tutorial will show you how to catch an exception using ASP.NET 2.0 and VB.NET

The .NET Framework offers a number of types that makes catching exceptions easy.

In this example we will be catching exceptions when trying to create a directory in the filesystem, so we will need the System.IO namespace. Our code will catch any exceptions when using the Directory.CreateDirectory() method.

Imports System.IO

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We'll put our code in the btnSubmit_Click() event.

When the btnSubmit_Click() event fires it runs a try block. The try block does two things: it lets exceptions thrown during the try block's execution to be caught by the catch block(s) below and ensures that execution can't leave the try block without running the finally block. In this example, we are specifying that our catch block handles exceptions of the type Exception.

Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click Try Directory.CreateDirectory(MapPath(".") & "\" & txtDir.Text) Catch e1 As Exception lblStatus.Text &= "There was an exception when creating the directory: " & txtDir.Text lblStatus.Text &= " in " & MapPath(".") & "\" End Try End Sub

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We have one textbox, a Submit button, and a label on the front end for user interaction. The front end .aspx page looks something like this:

<table width="600" border="0" align="center" cellpadding="5" cellspacing="1" bgcolor="#cccccc"> <tr> <td width="100" align="right" bgcolor="#eeeeee" class="header1"> Catching an Exception:</td> <td align="center" bgcolor="#FFFFFF"> Directory:<asp:TextBox ID="txtDir" runat="server"></asp:TextBox> <br /> <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="btnSubmit_Click" /><br /> &nbsp;<asp:label ID="lblStatus" runat="server"></asp:label></td> </tr> </table>

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The flow for the code behind page is as follows.

Imports System.IO Partial Class _Default Inherits System.Web.UI.Page Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click Try Directory.CreateDirectory(MapPath(".") & "\" & txtDir.Text) Catch e1 As Exception lblStatus.Text &= "There was an exception when creating the directory: " & txtDir.Text lblStatus.Text &= " in " & MapPath(".") & "\" End Try End Sub Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load End Sub End Class

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