When you create an application setting, you specify a name and value for the setting to be created. This lets you access the value of the setting in your application by using the AppSettings property of the ConfigurationSettings class. For example, if you define an application setting named AppName with a value that represents the name of your application, you might use it to set the heading of a page as shown in the following code example.

[Visual Basic]

labelPageHeading.Text = ConfigurationManager.AppSettings("AppName")

[C#]

labelPageHeading.Text = ConfigurationManager.AppSettings["AppName"];

If you want to do maintenance on the Web site, you can take it offline. This shuts the process down that is running the Web site so that the site no longer serves pages. You can then edit pages or other files without the possibility that a page will be requested while you are in the middle of your edits, potentially resulting in an error. Taking an application offline is also useful, if you are working with SQL Server Standard edition and want to swap or add an .mdf database file to the application. If the application is running, it cannot attach to new .mdf files.

When you have finished editing files or adding or changing .mdf files, you can put the application back online.

Some features of the Web site require that your application be able to send e-mail. To send e-mail, the application must have access to a Simple Mail Transfer Protocol (SMTP) server, which forwards e-mail from your application to the e-mail recipient.

IIS) includes an SMTP virtual server, although it is not installed by default. If you want to be able to send e-mail from your own computer, you can install the SMTP server by using Add or Remove Programs in the Microsoft Windows Control Panel. The SMTP server is available as a Windows Component as part of IIS. After you install the IIS SMTP server, you can configure it using the Internet Information Services Management Console. For detailed information about how to install the IIS SMTP virtual server, see the Knowledge Base (KB) search page.

Note:
If you install an SMTP server on the computer, you must take security precautions to make sure that the SMTP server is not vulnerable to being used as a spam server. For more information about how to help secure the IIS SMTP virtual server, go to Microsoft.com and search for SMTP security.

If you do not want to install the IIS SMTP server, or if the application will run on a different computer, contact the network or Web server administrator for information about configuration settings for an SMTP server.

The following table describes the SMTP settings.

You must have Administrative credentials on the computer where the Web application runs to change its debugging and tracing settings.

To manage the debugging and tracing features, clickConfigure debugging and tracing, and then set the following options:

• Enable Debugging

  Select this option to enable debugging for all pages in the Web site.

• Capture tracing information

  Select this option to enable tracing for all pages in the Web site. If this check box is selected, the remaining options on the page are enabled.

If you have set the option to capture tracing information, you can make the following choices:

• Display tracing information on individual pages

  Select this option to append tracing information to the bottom of Web pages on your site. If you do not display tracing information about individual pages, the information is still captured. To view trace information, you can request the Trace.axd page for the Web site, which acts as a tracing information viewer.

• Local requests only

  Select this option to view trace information only for request from the host Web server (localhost).

• All requests

  Select this option to view trace information from any computer.

Under Select the sort order for trace results, specify how you want to display trace information, as follows:

• By time

  Select this option to display trace information in the order that it is captured.

• By category

  Select this option to display trace information alphabetically within user-defined categories.

• Number of trace requests to cache

  Enter the number of trace requests to store on the server. You can view cached information by using the trace viewer (http://server/application/trace.axd). The default is 10. If you do not select the Most recent trace results option, and the limit is reached, trace is automatically disabled.

Under Select which trace results to cache, specify how you want to display trace output, as follows:

• Most recent trace results

  Select this option to display the most recent trace output and to discard older trace data beyond the limits that are indicated by Number of trace requests to cache.

• Oldest trace results

  Select this option to display trace data for requests until Number of trace requests to cache is reached.

Note:
When you are finished troubleshooting the Web site, disable debugging and tracing to get maximum performance from your Web application.

Security Note:
When tracing is enabled for a page, trace information might appear on any browser that makes a request for the page from the server. Because tracing displays sensitive information, such as the values of server variables, it can represent a security threat. Make sure that you disable page tracing for the page before publishing the Web application to a production server.

To configure a custom error page for the Web site, clickDefine default error page and then specify the following:

• Use the default error message

  Select this option to use the default error page.

• Specify a URL to use as the default error page

  Select this option to use a custom error page, and then choose the page to use.

The Application tab provides a simple Web interface for managing configuration settings that are stored in the Web.config file for your application.

Application Settings

<configuration>
    <appSettings>
        <add key="ApplicationName" value="MyApplication" />
    </appSettings>
</configuration>

Taking Applications Offline and Online

<configuration>
    <system.Web>
        <httpRuntime enable="False" />
    </system.Web>
</configuration> 

SMTP Settings

<configuration>
    <system.net>
        <mailSettings>
            <smtp>
                <network 
                    host="smtp.myhost.com" />
            </smtp>
        </mailSettings>
    </system.net>
</configuration>

Debugging and Tracing

<configuration>
    <system.Web>
        <customErrors defaultRedirect="~/myErrorPage.aspx" />
        <trace enabled="True" pageOutput="True" localOnly="True" 
                traceMode="SortByCategory"
            requestLimit="10" mostRecent="True" />
        <compilation debug="True" />
    </system.Web>
</configuration>

For more information, in the .NET Framework class reference and the ASP.NET Configuration Settings, see the following:

• ConfigurationSettings

• compilation Element (ASP.NET Settings Schema)

• customErrors Element (ASP.NET Settings Schema)

• trace Element (ASP.NET Settings Schema)

Concepts