9.2.1 Problem You have custom configuration information for your application that you would like to store in its web.config file. 9.2.2 Solution Modify the web.config file for your application by adding an <appSettings> section to contain the custom configuration settings. -
Locate the web.config file in the root directory of your application (or create one if it does not already exist). -
Add an <appSettings> element. -
Add <add> child elements along with key / value pairs to the <appSettings> element as required. -
In the code-behind class for your ASP.NET page, use the .NET language of your choice to access the <appSettings> key/value collection through the ConfigurationSettings object. Example 9-1 through Example 9-4 show the sample code we've written to implement this solution. Example 9-1 shows our web.config file with some key / value pairs. Example 9-2 shows the .aspx file for a web form that displays the configuration settings. Example 9-3 (VB) and Example 9-4 (C#) show the code-behind class that accesses the configuration settings using the ConfigurationSettings object. 9.2.3 Discussion ASP.NET lets you add and then access configuration information specific to your application to the web.config file by means of a special <appSettings> element. You can add application configuration information by adding an <add> child element for each parameter, setting the key attribute to the name of the configuration parameter, and then setting the value attribute to the value of the configuration parameter, as shown in Example 9-1. Notice that the <appSettings> element is not a child of <system.web> , like some of the other web.config elements we discuss in this chapter. Rather, it is a subsection all its own within the <configuration> section. When your application is started, ASP.NET creates a NameValueCollection from the key / value pairs in the <appSettings> section. You can access this NameValueCollection anywhere in your application through the ConfigurationSettings object. Any data that can be represented as a string can be stored in the <appSettings> section, but anything other than a string will need to be cast to the appropriate data type for use in your application.  | web.config allows any string for the value of a key / value pair. If the data is actually any nonstring data type, your code needs to include the appropriate exception handling for invalid data in the web.config file. | |
9.2.4 See Also Recipe 9.6 for how to store an application's configuration information in its own custom section in web.config Example 9-1. Application settings in web.config <?xml version="1.0" encoding="utf-8" ?> <configuration> <appSettings> <add key="defaultSortField" value="Title" /> <add key="defaultSortOrder" value="Ascending" /> <add key="defaultResultsPerPage" value="25" /> </appSettings> </configuration>
Example 9-2. Accessing application settings in web.config (.aspx) <%@ Page Language="vb" AutoEventWireup="false" Codebehind="CH09GetAppSettingsVB.aspx.vb" Inherits="ASPNetCookbook.VBExamples.CH09GetAppSettingsVB"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <title>Get Application Settings</title> <link rel="stylesheet" href="css/ASPNetCookbook.css"> </head> <body leftmargin="0" marginheight="0" marginwidth="0" topmargin="0"> <form id="frmConfiguration" method="post" runat="server"> <table width="100%" cellpadding="0" cellspacing="0" border="0"> <tr> <td align="center"> <img src="images/ASPNETCookbookHeading_blue.gif"> </td> </tr> <tr> <td class="dividerLine"> <img src="images/spacer.gif" height="6" border="0"></td> </tr> </table> <table width="90%" align="center" border="0"> <tr> <td><img src="images/spacer.gif" height="10" border="0"></td> </tr> <tr> <td align="center" class="PageHeading"> Application Configuration In web.config (VB) </td> </tr> <tr> <td><img src="images/spacer.gif" height="10" border="0"></td> </tr> <tr> <td align="center"> <table> <tr> <td class="LabelText">Sort Field: </td> <td class="LabelText"> <asp:Label ID="labSortField" Runat="server" /></td> </tr> <tr> <td class="LabelText">Sort Order: </td> <td class="LabelText"> <asp:Label ID="labSortOrder" Runat="server" /></td> </tr> <tr> <td class="LabelText">Number of Pages: </td> <td class="LabelText"> <asp:Label ID="labNumberOfPages" Runat="server" /></td> </tr> </table> </td> </tr> </table> </form> </body> </html>
Example 9-3. Accessing application settings in web.config (.vb) Option Explicit On Option Strict On '----------------------------------------------------------------------------- ' ' Module Name: CH09GetAppSettingsVB.aspx.vb ' ' Description: This module provides the code behind for the ' CH09GetAppSettingsVB.aspx page ' '***************************************************************************** Imports System Imports System.Configuration Namespace ASPNetCookbook.VBExamples Public Class CH09GetAppSettingsVB Inherits System.Web.UI.Page 'controls on the form Protected labSortField As System.Web.UI.WebControls.Label Protected labSortOrder As System.Web.UI.WebControls.Label Protected labNumberOfPages As System.Web.UI.WebControls.Label '************************************************************************* ' ' ROUTINE: Page_Load ' ' DESCRIPTION: This routine provides the event handler for the page load ' event. It is responsible for initializing the controls ' on the page. '------------------------------------------------------------------------- Private Sub Page_Load(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles MyBase.Load Dim resultsPerPage As Integer 'initialize labels on form from values in web.config labSortField.Text = ConfigurationSettings.AppSettings("defaultSortField") labSortOrder.Text = ConfigurationSettings.AppSettings("defaultSortOrder") 'get an integer value from web.config and do a little calculating resultsPerPage = _ CInt(ConfigurationSettings.AppSettings("defaultResultsPerPage")) labNumberOfPages.Text = Math.Ceiling(1234.0 / resultsPerPage).ToString( ) End Sub 'Page_Load End Class 'CH09GetAppSettingsVB End Namespace
Example 9-4. Accessing application settings in web.config (.cs) //---------------------------------------------------------------------------- // // Module Name: CH09GetAppSettingsCS.aspx.cs // // Description: This module provides the code behind for the // CH09GetAppSettingsCS.aspx page // //**************************************************************************** using System; using System.Configuration; namespace ASPNetCookbook.CSExamples { public class CH09GetAppSettingsCS : System.Web.UI.Page { // controls on the form protected System.Web.UI.WebControls.Label labSortField; protected System.Web.UI.WebControls.Label labSortOrder; protected System.Web.UI.WebControls.Label labNumberOfPages; //************************************************************************ // // ROUTINE: Page_Load // // DESCRIPTION: This routine provides the event handler for the page // load event. It is responsible for initializing the // controls on the page. //------------------------------------------------------------------------ private void Page_Load(object sender, System.EventArgs e) { int resultsPerPage; // initialize labels on form from values in web.config labSortField.Text = ConfigurationSettings.AppSettings["defaultSortField"]; labSortOrder.Text = ConfigurationSettings.AppSettings["defaultSortOrder"]; // get an integer value from web.config and do a little calculating resultsPerPage = Convert.ToInt32(ConfigurationSettings.AppSettings["defaultResultsPerPage"]); labNumberOfPages.Text = Math.Ceiling(1234.0 / resultsPerPage).ToString( ); } // Page_Load } // CH09GetAppSettingsCS }
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