Custom Error Handling in ASP.NET

.Net provides number of ways to manage and handle errors. Generally we use try..catch block to handle the error and show the error message in a label. Instead of showing the error in that page, we can show the error in another page with the customized manner, so that it can be seem more professional.

Steps:

1.Create an ASP.NET web site.
2.Add a class ErrorPage.cs in the App_Code folder.
3.Add the following variable in the ErrorPage.cs file

//Declare the private HttpApplication variable
private HttpApplication _application;

void IHttpModule.Init (HttpApplication application)
{
_application = application;

//check whether the ErrorHandling values is Application type set in the web.config
//file or not. If yes then declare an EventHandler 
if (GetValue("ErrorHandling") == "Application")
_application.Error += new EventHandler(ErrorPageHandler);

}


private void ErrorPageHandler(Object sender, EventArgs e)
{
//fetch the error
ProcessException(_application.Server.GetLastError());
}

//store the error in the Cache
private void ProcessException(Exception exception)
{
HttpContext.Current.Cache["Error"] = HttpContext.Current.Request.Url.ToString();
HttpContext.Current.Cache["ErrorMsg"] = exception.Message;
HttpContext.Current.Cache["StackTrace"] = exception.StackTrace;

HttpContext.Current.Response.Redirect(GetValue("SiteUrl") + "/Error.aspx");
}


//fetch the value from the web.config file
public string GetValue(string Key)
{
string ret = System.Web.Configuration.WebConfigurationManager.AppSettings[Key];

return ret;
}
public void Dispose()
{
}

4.Create an Error.aspx page and add the following html code

<asp:table width="100%" align="center" >

<asp:tr>
<asp:td style="text-align: left; font-weight: bold">
Error In
<asp:/td>
<asp:/tr>
<asp:tr>
<asp:td  style="text-align: left; font-weight: bold">
<asp:asp:Label ID="lblError" runat="server" CssClass="x-panel-mc-font"><asp:/asp:Label>
<asp:/td>
<asp:/tr>
<asp:tr>
<asp:td  style="text-align: left; font-weight: bold">
  
<asp:/td>
<asp:/tr>
<asp:tr>
<asp:td style="text-align: left; font-weight: bold">
Error Message
<asp:/td>
<asp:/tr>
<asp:tr>
<asp:td  style="text-align: left;">
<asp:asp:Label ID="lblErrorMsg" runat="server" CssClass="x-panel-mc-font"><asp:/asp:Label>
<asp:/td>
<asp:/tr>
<asp:tr>
<asp:td  style="text-align: left;">
  
<asp:/td>
<asp:/tr>
<asp:tr>
<asp:td style="text-align: left; font-weight: bold">
Stack Track
<asp:/td>
<asp:/tr>
<asp:tr>
<asp:td  style="text-align: left;">
<asp:asp:Label ID="lblStackTrace" runat="server" CssClass="x-panel-mc-font"><asp:/asp:Label>
<asp:/td>
<asp:/tr>
<asp:tr>
<asp:td  style="text-align: left;">
  
<asp:/td>
<asp:/tr>
<asp:/table>

Here I have used 3 lables to show the page name (from where error is generated), Error Message and Stack Track.

5.Add the following code in the Error.aspx.cs page

protected void Page_Load(object sender, EventArgs e)
{
if (Cache["Error"] != null)
lblError.Text = Cache["Error"].ToString();
if (Cache["ErrorMsg"] != null)
lblErrorMsg.Text = Cache["ErrorMsg"].ToString();
if (Cache["StackTrace"] != null)
lblStackTrace.Text = Cache["StackTrace"].ToString();

}

Fetched the errors from the Cache and showing in the labels.

6.In the default.aspx page add a button control, and add the following code in the button click event.

int a = 1, b = 0;
int c = a / b;

Generating the error.

7.Add the following setting in the web.config file

<asp:appSettings>
<asp:add key="SiteUrl" value="http://localhost:1371/CustomeErrorHandling"/>
<asp:add key="ErrorHandling" value="Application"/>
<asp:/appSettings>

And add in the <httpModules> section

<asp:add type="ErrorPage" name="ErrorPageHandler">

8.Now run the application



9.Click on the Show Error button, then the error will be show in the following manner.



Note: Do not use try..catch block in the code behind page, If you use then custome error will not work. i.e. If I write the code in the following manner

try
{
int a = 1, b = 0;
int c = a / b;
}
catch
{ }

Then the error page will not show.

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