Complete Example for Error Handlers

  • Article

This code example includes elements for both page-level and application-level exception handling.

Code Example Files

The example consists of the following files:

  • Web.config

  • Global.asax

  • Default.aspx

  • ExceptionUtility (to be put in the App_Code folder)

  • GenericErrorPage.aspx

  • HttpErrorPage.aspx

  • Http404ErrorPage.aspx

  • DefaultRedirectErrorPage.aspx

Web.config

The following example shows the Web.config file. The customErrors section specifies how to handle errors that occur with file types that are mapped to ASP.NET, such as .aspx, .asmx, and .ashx files. (In IIS 6.0 and in IIS 7.0 in classic mode, static content files such as .html and .jpg files are not mapped to ASP.NET.)

The settings in the example customErrors section cause any unhandled HTTP 404 (file not found) errors to be directed to the Http404ErrorPage.aspx file. These HTTP 404 errors would occur if a request were made for an .aspx file, .asmx file, and so on and if the requested file did not exist. All other unhandled errors in ASP.NET files are directed to the DefaultRedirectErrorPage.aspx file.

If static content files are not handled by ASP.NET, a request for a nonexistent .html or .jpg file does not cause a redirect to the Http404ErrorPage.aspx file. If you want ASP.NET to handle requests for all file types, you can configure IIS to map file-name extensions to ASP.NET.

Note

In the example, the mode attribute is set to "On" so that you can error messages when you run the example in Visual Studio. In a production environment, this setting would normally be "RemoteOnly". ASP.NET then renders error pages to external users. If a request is made on the server computer (localhost), ASP.NET renders a page with detailed error information.

<configuration>
  <appSettings/>
  <connectionStrings/>
  <system.web>
    <compilation debug="true" />

    <!-- Turn on Custom Errors -->
    <customErrors mode="On" 
      defaultRedirect="DefaultRedirectErrorPage.aspx">
      <error statusCode="404" redirect="Http404ErrorPage.aspx"/>
    </customErrors>

  </system.web>
</configuration>

Global.asax

The following example shows the Global.asax file

Security noteSecurity Note:

Never set the mode attribute in the customErrors element to "Off" in the Web.config file if you have not created an Application_Error handler in the Global.asax file. If the mode is set to "Off," potentially compromising information about your Web site can be exposed to anyone who can cause an error to occur on your site.

 
Sub Application_Error(ByVal sender AsObject, ByVal e As EventArgs)
  ' Code that runs when an unhandled error occurs
  ' Get the exception object.Dim exc As Exception = Server.GetLastError

  ' Handle HTTP errors (avoid trapping HttpUnhandledException  ' which is generated when a non-HTTP exception   ' such as the ones generated by buttons 1-3 in   ' Default.aspx is not handled at the page level).If (exc.GetTypeIsGetType(HttpException)) Then    ' The Complete Error Handling Example generates    ' some errors using URLs with "NoCatch" in them;    ' ignore these here to simulate what would happen    ' if a global.asax handler were not implemented.If exc.Message.Contains("NoCatch") Or exc.Message.Contains("maxUrlLength") ThenReturnEndIf
    'Redirect HTTP errors to HttpError page
    Server.Transfer("HttpErrorPage.aspx")
  EndIf
  ' For other kinds of errors give the user some information  ' but stay on the default page
  Response.Write("<h2>Global Page Error</h2>" & vbLf)
  Response.Write("<p>" & exc.Message + "</p>" & vbLf)
  Response.Write(("Return to the <a href='Default.aspx'>" _
    & "Default Page</a>" & vbLf))

  ' Log the exception and notify system operators
  ExceptionUtility.LogException(exc, "DefaultPage")
  ExceptionUtility.NotifySystemOps(exc)

  ' Clear the error from the server
  Server.ClearError()
EndSub

void Application_Error(object sender, EventArgs e)
{
  // Code that runs when an unhandled error occurs// Get the exception object.
  Exception exc = Server.GetLastError();

  // Handle HTTP errorsif (exc.GetType() == typeof(HttpException))
  {
    // The Complete Error Handling Example generates// some errors using URLs with "NoCatch"in them;
    // ignore these here to simulate what would happen// if a global.asax handler were not implemented.if (exc.Message.Contains("NoCatch") || exc.Message.Contains("maxUrlLength"))
      return;

    //Redirect HTTP errors to HttpError page
    Server.Transfer("HttpErrorPage.aspx");
  }

  // For other kinds of errors give the user some information// but stay on the default page
  Response.Write("<h2>Global Page Error</h2>\n");
  Response.Write(
      "<p>" + exc.Message + "</p>\n");
  Response.Write("Return to the <a href='Default.aspx'>" +
      "Default Page</a>\n");

  // Log the exception and notify system operators
  ExceptionUtility.LogException(exc, "DefaultPage");
  ExceptionUtility.NotifySystemOps(exc);

  // Clear the error from the server
  Server.ClearError();
}

ExceptionUtility

The following example shows the ExceptionUtility file. Error logs might be directed to the computer's ErrorLog file, or, if the computer is part of a Web farm, the error log might be recorded in a globally available text file, or even a database. You might also need to immediately notify system administrators of a problem.

The ExceptionUtility class in the example has two static methods: one to log the exception, and one to notify system administrators. How those methods are implemented in your code depends on the needs of your organization. For this example, you must grant write permissions to the ASP.NET worker process account (by default, this is NETWORK SERVICE) for the App_Data folder to enable the application to write to the error log.

Imports System
Imports System.IO
Imports System.Web

' Create our own utility for exceptionsPublicNotInheritableClass ExceptionUtility

    ' All methods are static, so this can be privatePrivateSubNew()
        MyBase.New()
    EndSub
    ' Log an ExceptionPublicSharedSub LogException(ByVal exc As Exception, ByVal source AsString)
        ' Include enterprise logic for logging exceptions        ' Get the absolute path to the log fileDim logFile = "App_Data/ErrorLog.txt"
        logFile = HttpContext.Current.Server.MapPath(logFile)

        ' Open the log file for append and write the logDim sw = New StreamWriter(logFile, True)
        sw.WriteLine("**** " & DateTime.Now & " ****")
        If exc.InnerException IsNotNothingThen
            sw.Write("Inner Exception Type: ")
            sw.WriteLine(exc.InnerException.GetType.ToString)
            sw.Write("Inner Exception: ")
            sw.WriteLine(exc.InnerException.Message)
            sw.Write("Inner Source: ")
            sw.WriteLine(exc.InnerException.Source)
            If exc.InnerException.StackTrace IsNotNothingThen
                sw.WriteLine("Inner Stack Trace: ")
                sw.WriteLine(exc.InnerException.StackTrace)
            EndIfEndIf
        sw.Write("Exception Type: ")
        sw.WriteLine(exc.GetType.ToString)
        sw.WriteLine("Exception: " & exc.Message)
        sw.WriteLine("Source: " & source)
        If exc.StackTrace IsNotNothingThen
            sw.WriteLine("Stack Trace: ")
            sw.WriteLine(exc.StackTrace)
        EndIf
        sw.WriteLine()
        sw.Close()
    EndSub
    ' Notify System Operators about an exceptionPublicSharedSub NotifySystemOps(ByVal exc As Exception)
        ' Include code for notifying IT system operatorsEndSubEndClass

using System;
using System.IO;
using System.Web;

// Create our own utility for exceptionspublicsealedclass ExceptionUtility
{
    // All methods are static, so this can be privateprivate ExceptionUtility()
    { }

    // Log an Exceptionpublicstaticvoid LogException(Exception exc, string source)
    {
        // Include enterprise logic for logging exceptions// Get the absolute path to the log filestring logFile = "App_Data/ErrorLog.txt";
        logFile = HttpContext.Current.Server.MapPath(logFile);

        // Open the log file for append and write the log
        StreamWriter sw = new StreamWriter(logFile, true);
        sw.WriteLine("********** {0} **********", DateTime.Now);
        if (exc.InnerException != null)
        {
            sw.Write("Inner Exception Type: ");
            sw.WriteLine(exc.InnerException.GetType().ToString());
            sw.Write("Inner Exception: ");
            sw.WriteLine(exc.InnerException.Message);
            sw.Write("Inner Source: ");
            sw.WriteLine(exc.InnerException.Source);
            if (exc.InnerException.StackTrace != null)
            {
                sw.WriteLine("Inner Stack Trace: ");
                sw.WriteLine(exc.InnerException.StackTrace);
            }
        }
        sw.Write("Exception Type: ");
        sw.WriteLine(exc.GetType().ToString());
        sw.WriteLine("Exception: " + exc.Message);
        sw.WriteLine("Source: " + source);
        sw.WriteLine("Stack Trace: ");
        if (exc.StackTrace != null)
        {
            sw.WriteLine(exc.StackTrace);
            sw.WriteLine();
        }
        sw.Close();
    }

    // Notify System Operators about an exceptionpublicstaticvoid NotifySystemOps(Exception exc)
    {
        // Include code for notifying IT system operators
    }
}

Default.aspx

The following example shows the Default.aspx page. This file provides several buttons, each of which raises a different exception. The Page_Error handler on the page displays an error page and logs some of these errors. Unhandled errors are passed to the Application_Error handler in the Global.asax file. The Application_Error handler displays an error page and logs some of the remaining errors. Any errors that are still not handled are directed to the page indicated by the customErrors section of Web.config file.

<%@ Page Language="VB" %>

<script runat="server">
  ProtectedSub Submit_Click(ByVal sender AsObject, ByVal e As EventArgs)
    Dim arg AsString = CType(sender, Button).CommandArgument
    SelectCase (arg)
      Case"1"        ' Exception handled on the Generic Error PageThrowNew InvalidOperationException("Button 1 was clicked")
        ExitSelectCase"2"        ' Exception handled on the current pageThrowNew ArgumentOutOfRangeException("Button 2 was clicked")
        ExitSelectCase"3"        ' Exception handled by Application_ErrorThrowNew Exception("Button 3 was clicked")
        ExitSelectCase"4"        ' Exception handled on the Http 404 Error Page
        Response.Redirect("NonexistentPage.aspx")
        ExitSelectCase"5"        ' Exception handled on the Http Error Page
        Response.Redirect("NonexistentPage-NoCatch.aspx")
        ExitSelectCase"6"        ' Exception handled on the Default Redirect Error Page
        Response.Redirect("NonexistentPage-NoCatch.aspx/" + new string('x',500))
        ExitSelectEndSelectEndSubPrivateSub Page_Error(ByVal sender AsObject, ByVal e As EventArgs)
    ' Get last error from the serverDim exc As Exception = Server.GetLastError

    ' Handle exceptions generated by Button 1IfTypeOf exc Is InvalidOperationException Then      ' Pass the error on to the Generic Error page
      Server.Transfer("GenericErrorPage.aspx", True)

    ' Handle exceptions generated by Button 2ElseIfTypeOf exc Is ArgumentOutOfRangeException Then      ' Give the user some information, but      ' stay on the default page
      Response.Write("<h2>Default Page Error</h2>" & vbLf)
      Response.Write(("<p>Provide as much information here as is " _
        & "appropriate to show to the client.</p>" & vbLf))
      Response.Write(("Return to the <a href='Default.aspx'>" _
        & "Default Page</a>" & vbLf))
      ' Log the exception and notify system operators
      ExceptionUtility.LogException(exc, "DefaultPage")
      ExceptionUtility.NotifySystemOps(exc)
      ' Clear the error from the server
      Server.ClearError()
    Else      ' Pass the error on to the default global handlerEndIfEndSub

</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head id="Head1" runat="server">
  <title>Exception Handler Page</title>
</head>
<body>
  <form id="form1" runat="server">
  <div>
    <h2>
      Default Page</h2>
    <p>
      Click this button to create an InvalidOperationException.<br />
      Page_Error will catch this and redirect to 
        GenericErrorPage.aspx.<br />
      <asp:Button ID="Submit1" runat="server" 
        CommandArgument="1" OnClick="Submit_Click"
        Text="Button 1" />
    </p>
    <p>
      Click this button to create an ArgumentOutOfRangeException.<br />
      Page_Error will catch this and handle the error.<br />
      <asp:Button ID="Submit2" runat="server" 
        CommandArgument="2" OnClick="Submit_Click"
        Text="Button 2" />
    </p>
    <p>
      Click this button to create a generic Exception.<br />
      Application_Error will catch this and handle the error.<br />
      <asp:Button ID="Submit3" runat="server" 
        CommandArgument="3" OnClick="Submit_Click"
        Text="Button 3" />
    </p>
    <p>
      Click this button to create an HTTP 404 (not found) error.<br />
      Application_Error will catch this 
      and redirect to HttpErrorPage.aspx.<br />
      <asp:Button ID="Submit4" runat="server" 
        CommandArgument="4" OnClick="Submit_Click"
        Text="Button 4" />
    </p>
    <p>
      Click this button to create an HTTP 404 (not found) error.<br />
      Application_Error will catch this but will not take any action on it, 
      and ASP.NET will redirect to Http404ErrorPage.aspx. 
      The original exception object will not be available.<br />
      <asp:Button ID="Submit5" runat="server" 
        CommandArgument="5" OnClick="Submit_Click"
        Text="Button 5" />
    </p>
    <p>
      Click this button to create an HTTP 400 (invalid url) error.<br />
      Application_Error will catch this but will not take any action on it,
      and ASP.NET will redirect to DefaultRedirectErrorPage.aspx. 
      The original exception object will not be available.<br />
      <asp:Button ID="Button1" runat="server" 
        CommandArgument="6" OnClick="Submit_Click"
        Text="Button 6" />
    </p>
  </div>
  </form>
</body>
</html>

<%@ Page Language="C#" %>

<script runat="server">
  protectedvoid Submit_Click(object sender, EventArgs e)
  {
    string arg = ((Button)sender).CommandArgument;

    switch (arg)
    {
      case"1":
        {
          // Exception handled on the Generic Error Pagethrownew InvalidOperationException("Button 1 was clicked");
          break;
        }
      case"2":
        {
          // Exception handled on the current pagethrownew ArgumentOutOfRangeException("Button 2 was clicked");
          break;
        }
      case"3":
        {
          // Exception handled by Application_Errorthrownew Exception("Button 3 was clicked");
          break;
        }
      case"4":
        {
          // Exception handled on the Http 404 Error Page
          Response.Redirect("NonexistentPage.aspx");
          break;
        }
      case"5":
        {
          // Exception handled on the Http Error Page
          Response.Redirect("NonexistentPage-NoCatch.aspx");
          break;
        }
      case"6":
        {
          // Exception handled on the Generic Http Error Page
            Response.Redirect("NonexistentPage-NoCatch.aspx/" + newstring('x', 500));
          break;
        }
    }
  }
  privatevoid Page_Error(object sender, EventArgs e)
  {
    // Get last error from the server
    Exception exc = Server.GetLastError();

    // Handle exceptions generated by Button 1if (exc is InvalidOperationException)
    {
      // Pass the error on to the Generic Error page
      Server.Transfer("GenericErrorPage.aspx", true);
    }

    // Handle exceptions generated by Button 2elseif (exc is ArgumentOutOfRangeException)
    {
      // Give the user some information, but// stay on the default page
      Response.Write("<h2>Default Page Error</h2>\n");
      Response.Write("<p>Provide as much information here as is " +
        "appropriate to show to the client.</p>\n");
      Response.Write("Return to the <a href='Default.aspx'>" +
          "Default Page</a>\n");

      // Log the exception and notify system operators
      ExceptionUtility.LogException(exc, "DefaultPage");
      ExceptionUtility.NotifySystemOps(exc);

      // Clear the error from the server
      Server.ClearError();
    }
    else
    {
      // Pass the error on to the default global handler
    }
  }
</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head id="Head1" runat="server">
  <title>Exception Handler Page</title>
</head>
<body>
  <form id="form1" runat="server">
  <div>
    <h2>
      Default Page</h2>
    <p>
      Click this button to create an InvalidOperationException.<br />
      Page_Error will catchthis and redirect to 
      GenericErrorPage.aspx.<br />
      <asp:Button ID="Submit1" runat="server" 
        CommandArgument="1" OnClick="Submit_Click"
        Text="Button 1" />
    </p>
    <p>
      Click this button to create an ArgumentOutOfRangeException.<br />
      Page_Error will catchthis and handle the error.<br />
      <asp:Button ID="Submit2" runat="server" 
        CommandArgument="2" OnClick="Submit_Click"
        Text="Button 2" />
    </p>
    <p>
      Click this button to create a generic Exception.<br />
      Application_Error will catchthis and handle the error.<br />
      <asp:Button ID="Submit3" runat="server" 
        CommandArgument="3" OnClick="Submit_Click"
        Text="Button 3" />
    </p>
    <p>
      Click this button to create an HTTP 404 (not found) error.<br />
      Application_Error will catchthis 
      and redirect to HttpErrorPage.aspx.<br />
      <asp:Button ID="Submit4" runat="server" 
      CommandArgument="4" OnClick="Submit_Click"
        Text="Button 4" />
    </p>
    <p>
      Click this button to create an HTTP 404 (not found) error.<br />
      Application_Error will catchthis 
      but will not take any action on it, and ASP.NET
      will redirect to Http404ErrorPage.aspx. 
      The original exception object will not be
      available.<br />
      <asp:Button ID="Submit5" runat="server" 
        CommandArgument="5" OnClick="Submit_Click"
        Text="Button 5" />
    </p>
    <p>
      Click this button to create an HTTP 400 (invalid url) error.<br />
      Application_Error will catchthis 
      but will not take any action on it, and ASP.NET
      will redirect to DefaultRedirectErrorPage.aspx. 
      The original exception object will not
      be available.<br />
      <asp:Button ID="Button1" runat="server" 
        CommandArgument="6" OnClick="Submit_Click"
        Text="Button 6" />
    </p>
  </div>
  </form>
</body>
</html>

GenericErrorPage.aspx

The following example shows the GenericErrorPage.aspx page. This page creates a safe message that it displays to remote users. For local users (typically developers and testers of the application), the page displays a complete exception report. The Page_Error handler redirects InvalidOperationException errors to this page.

<%@ Page Language="VB" %>

<script runat="server">
  Dim ex As Exception = NothingProtectedSub Page_Load(ByVal sender AsObject, ByVal e As EventArgs)
    ' Get the last error from the serverDim ex As Exception = Server.GetLastError

    ' Create a safe messageDim safeMsg = "A problem has occurred in the web site. "
    ' Show Inner Exception fields for local accessIf ex.InnerException IsNotNothingThen
      innerTrace.Text = ex.InnerException.StackTrace
      InnerErrorPanel.Visible = Request.IsLocal
      innerMessage.Text = ex.InnerException.Message
    EndIf
    ' Show Trace for local accessIf Request.IsLocal Then
      exTrace.Visible = TrueElse
      ex = New Exception(safeMsg, ex)
    EndIf
    ' Fill the page fields
    exMessage.Text = ex.Message
    exTrace.Text = ex.StackTrace

    ' Log the exception and notify system operators
    ExceptionUtility.LogException(ex, "Generic Error Page")
    ExceptionUtility.NotifySystemOps(ex)

    ' Clear the error from the server
    Server.ClearError()
  EndSub

</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head id="Head1" runat="server">
  <title>Generic Error Page</title>
</head>
<body>
  <form id="form1" runat="server">
  <div>
    <h2>
      Generic Error Page</h2>
    <asp:Panel ID="InnerErrorPanel" runat="server" Visible="false">
      <p>
        Inner Error Message:<br />
        <asp:Label ID="innerMessage" runat="server" Font-Bold="true" 
          Font-Size="Large" /><br />
      </p>
      <pre>
        <asp:Label ID="innerTrace" runat="server" />
      </pre>
    </asp:Panel>
    <p>
      Error Message:<br />
      <asp:Label ID="exMessage" runat="server" Font-Bold="true" 
        Font-Size="Large" />
    </p>
    <pre>
      <asp:Label ID="exTrace" runat="server" Visible="false" />
    </pre>
    <br />
    Return to the <a href='Default.aspx'>Default Page</a>
  </div>
  </form>
</body>
</html>

<%@ Page Language="C#" %>

<script runat="server">
  protected Exception ex = null;

  protectedvoid Page_Load(object sender, EventArgs e)
  {
    // Get the last error from the server
    Exception ex = Server.GetLastError();

    // Create a safe messagestring safeMsg = "A problem has occurred in the web site. ";

    // Show Inner Exception fields for local accessif (ex.InnerException != null)
    {
      innerTrace.Text = ex.InnerException.StackTrace;
      InnerErrorPanel.Visible = Request.IsLocal;
      innerMessage.Text = ex.InnerException.Message;
    }
    // Show Trace for local accessif (Request.IsLocal)
      exTrace.Visible = true;
    else
      ex = new Exception(safeMsg, ex);

    // Fill the page fields
    exMessage.Text = ex.Message;
    exTrace.Text = ex.StackTrace;

    // Log the exception and notify system operators
    ExceptionUtility.LogException(ex, "Generic Error Page");
    ExceptionUtility.NotifySystemOps(ex);

    // Clear the error from the server
    Server.ClearError();
  }
</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head id="Head1" runat="server">
  <title>Generic Error Page</title>
</head>
<body>
  <form id="form1" runat="server">
  <div>
    <h2>
      Generic Error Page</h2>
    <asp:Panel ID="InnerErrorPanel" runat="server" Visible="false">
      <p>
        Inner Error Message:<br />
        <asp:Label ID="innerMessage" runat="server" Font-Bold="true" 
          Font-Size="Large" /><br />
      </p>
      <pre>
        <asp:Label ID="innerTrace" runat="server" />
      </pre>
    </asp:Panel>
    <p>
      Error Message:<br />
      <asp:Label ID="exMessage" runat="server" Font-Bold="true" 
        Font-Size="Large" />
    </p>
    <pre>
      <asp:Label ID="exTrace" runat="server" Visible="false" />
    </pre>
    <br />
    Return to the <a href='Default.aspx'> Default Page</a>
  </div>
  </form>
</body>
</html>

HttpErrorPage.aspx

The following example shows the HttpErrorPage.aspx page. This page also creates a safe message that depends on the value of the error code, which it displays to remote users. For local users, the page displays a complete exception report. The Application_Error handler redirects HttpException errors to this page.

<%@ Page Language="VB" %>

<script runat="server">
  Dim ex As HttpException = NothingProtectedSub Page_Load(ByVal sender AsObject, ByVal e As EventArgs)
    ex = CType(Server.GetLastError, HttpException)
    Dim httpCode AsInteger = ex.GetHttpCode

    ' Filter for Error Codes and set textIf ((httpCode >= 400) AndAlso (httpCode < 500)) Then
      ex = New HttpException(httpCode, _
        "Safe message for 4xx HTTP codes.", ex)
    ElseIf (httpCode > 499) Then
      ex = New HttpException(ex.ErrorCode, _
        "Safe message for 5xx HTTP codes.", ex)
    Else
      ex = New HttpException(httpCode, _
        "Safe message for unexpected HTTP codes.", ex)
    EndIf
    ' Log the exception and notify system operators
    ExceptionUtility.LogException(ex, "HttpErrorPage")
    ExceptionUtility.NotifySystemOps(ex)

    ' Fill the page fields
    exMessage.Text = ex.Message
    exTrace.Text = ex.StackTrace

    ' Show Inner Exception fields for local accessIf ex.InnerException IsNotNothingThen
      innerTrace.Text = ex.InnerException.StackTrace
      InnerErrorPanel.Visible = Request.IsLocal
      innerMessage.Text = _
        "HTTP " & httpCode & ": " & ex.InnerException.Message
    EndIf
    ' Show Trace for local access
    exTrace.Visible = Request.IsLocal
    ' Clear the error from the server
    Server.ClearError()
  EndSub

</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head id="Head1" runat="server">
  <title>Http Error Page</title>
</head>
<body>
  <form id="form1" runat="server">
  <div>
    <h2>
      Http Error Page</h2>
    <asp:Panel ID="InnerErrorPanel" runat="server" Visible="false">
      <asp:Label ID="innerMessage" runat="server" Font-Bold="true" 
        Font-Size="Large" /><br />
      <pre>
        <asp:Label ID="innerTrace" runat="server" />
      </pre>
    </asp:Panel>
    Error Message:<br />
    <asp:Label ID="exMessage" runat="server" Font-Bold="true" 
      Font-Size="Large" />
    <pre>
      <asp:Label ID="exTrace" runat="server" Visible="false" />
    </pre>
    <br />
    Return to the <a href='Default.aspx'>Default Page</a>
  </div>
  </form>
</body>
</html>

<%@ Page Language="C#" %>

<script runat="server">
  protected HttpException ex = null;

  protectedvoid Page_Load(object sender, EventArgs e)
  {
    ex = (HttpException)Server.GetLastError();
    int httpCode = ex.GetHttpCode();

    // Filter for Error Codes and set textif (httpCode >= 400 && httpCode < 500)
      ex = new HttpException
          (httpCode, "Safe message for 4xx HTTP codes.", ex);
    elseif (httpCode > 499)
      ex = new HttpException
          (ex.ErrorCode, "Safe message for 5xx HTTP codes.", ex);
    else
      ex = new HttpException
          (httpCode, "Safe message for unexpected HTTP codes.", ex);

    // Log the exception and notify system operators
    ExceptionUtility.LogException(ex, "HttpErrorPage");
    ExceptionUtility.NotifySystemOps(ex);

    // Fill the page fields
    exMessage.Text = ex.Message;
    exTrace.Text = ex.StackTrace;

    // Show Inner Exception fields for local accessif (ex.InnerException != null)
    {
      innerTrace.Text = ex.InnerException.StackTrace;
      InnerErrorPanel.Visible = Request.IsLocal;
      innerMessage.Text = string.Format("HTTP {0}: {1}",
        httpCode, ex.InnerException.Message);
    }
    // Show Trace for local access
    exTrace.Visible = Request.IsLocal;

    // Clear the error from the server
    Server.ClearError();
  }
</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head id="Head1" runat="server">
  <title>Http Error Page</title>
</head>
<body>
  <form id="form1" runat="server">
  <div>
    <h2>
      Http Error Page</h2>
    <asp:Panel ID="InnerErrorPanel" runat="server" Visible="false">
      <asp:Label ID="innerMessage" runat="server" Font-Bold="true" 
        Font-Size="Large" /><br />
      <pre>
        <asp:Label ID="innerTrace" runat="server" />
      </pre>
    </asp:Panel>
    Error Message:<br />
    <asp:Label ID="exMessage" runat="server" Font-Bold="true" 
      Font-Size="Large" />
    <pre>
      <asp:Label ID="exTrace" runat="server" Visible="false" />
    </pre>
    <br />
    Return to the <a href='Default.aspx'>Default Page</a>
  </div>
  </form>
</body>
</html>

Http404ErrorPage.aspx

The following example shows the Http404ErrorPage.aspx page. ASP.NET redirects unhandled HTTP 404 (file not found) errors to this page. The page displays the same message to remote and local users.

<%@ Page Language="VB" %>

<script runat="server">
  Dim ex As HttpException

  ProtectedSub Page_Load(ByVal sender AsObject, ByVal e As EventArgs)
    ' Log the exception and notify system operators
    ex = New HttpException("defaultRedirect")
    ExceptionUtility.LogException(ex, "Caught in DefaultRedirectErrorPage")
    ExceptionUtility.NotifySystemOps(ex)
  EndSub

</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head id="Head1" runat="server">
  <title>HTTP 404 Error Page</title>
</head>
<body>
  <form id="form1" runat="server">
  <div>
    <h2>
      HTTP 404 Error Page</h2>
    Standard error message suitable for file not found errors. 
    The original exception object is not available, 
    but the original requested URL is in the query string.<br />
    <br />
    Return to the <a href='Default.aspx'> Default Page</a>
  </div>
  </form>
</body>
</html>

<%@ Page Language="C#" %>

<script runat="server">
  protected HttpException ex = null;

  protectedvoid Page_Load(object sender, EventArgs e)
  {
    // Log the exception and notify system operators
    ex = new HttpException("HTTP 404");
    ExceptionUtility.LogException(ex, "Caught in Http404ErrorPage");
    ExceptionUtility.NotifySystemOps(ex);
  }
</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head id="Head1" runat="server">
  <title>HTTP 404 Error Page</title>
</head>
<body>
  <form id="form1" runat="server">
  <div>
    <h2>
      HTTP 404 Error Page</h2>
    Standard error message suitable for file not found errors. 
    The original exception objectis not available, 
    but the original requested URL isin the query string.<br />
    <br />
    Return to the <a href='Default.aspx'> Default Page</a>
  </div>
  </form>
</body>
</html>

DefaultRedirectErrorPage.aspx

The following example shows the DefaultRedirectErrorPage.aspx page. ASP.NET redirects any unhandled errors except HTTP 404 errors to this page. The page displays the same message to remote and local users.

<%@ Page Language="VB" %>

<script runat="server">
  Dim ex As HttpException

  ProtectedSub Page_Load(ByVal sender AsObject, ByVal e As EventArgs)
    ' Log the exception and notify system operators
    ex = New HttpException("defaultRedirect")
    ExceptionUtility.LogException(ex, "Caught in DefaultRedirectErrorPage")
    ExceptionUtility.NotifySystemOps(ex)
  EndSub

</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head id="Head1" runat="server">
  <title>DefaultRedirect Error Page</title>
</head>
<body>
  <form id="form1" runat="server">
  <div>
    <h2>
      DefaultRedirect Error Page</h2>
    Standard error message suitable for all unhandled errors. 
    The original exception object is not available.<br />
    <br />
    Return to the <a href='Default.aspx'>Default Page</a>
  </div>
  </form>
</body>
</html>

<%@ Page Language="C#" %>

<script runat="server">
  protected HttpException ex = null;

  protectedvoid Page_Load(object sender, EventArgs e)
  {
    // Log the exception and notify system operators
    ex = new HttpException("defaultRedirect");
    ExceptionUtility.LogException(ex, "Caught in DefaultRedirectErrorPage");
    ExceptionUtility.NotifySystemOps(ex);
  }
</script>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head id="Head1" runat="server">
  <title>DefaultRedirect Error Page</title>
</head>
<body>
  <form id="form1" runat="server">
  <div>
    <h2>
      DefaultRedirect Error Page</h2>
    Standard error message suitable for all unhandled errors. 
    The original exception objectis not available.<br />
    <br />
    Return to the <a href='Default.aspx'> Default Page</a>
  </div>
  </form>
</body>
</html>

See Also

Tasks

How to: Handle Page-Level Errors

How to: Handle Application-Level Errors

Other Resources

Error Handling in ASP.NET Pages and Applications

Rich Custom Error Handling with ASP.NET