ASP.NET 4 Unleased - p 157 potx

After you make this modification to a remote server, you can retrieve and modify config-uration settings on the remote server by using one of the Open methods exposed by the WebConfigura

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NOTE

If you open the SDK Command Prompt or the Visual Studio Command Prompt, you

don’t need to navigate to the Microsoft.NET folder to execute the aspnet_regiis tool

After you make this modification to a remote server, you can retrieve (and modify)

config-uration settings on the remote server by using one of the Open methods exposed by the

WebConfigurationManager class For example, the page in Listing 34.13 contains a form

that enables you to enter a server, username, and password When you submit the form,

the page connects to the remote server and retrieves its Machine.config file The page

displays the current value of the remote server’s authentication mode (see Figure 34.8)

FIGURE 34.8 Changing configuration settings for a remote server

LISTING 34.13 ShowConfigRemote.aspx

<%@ Page Language=”C#” %>

<%@ Import Namespace=”System.Web.Configuration” %>

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN”

“http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”>

protected void btnSubmit_Click(object sender, EventArgs e)

{

try

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{

Configuration config = WebConfigurationManager.OpenMachine

➥Configuration(null, txtServer.Text, txtUserName.Text, txtPassword.Text);

AuthenticationSection section = (AuthenticationSection)config

➥GetSection(“system.web/authentication”);

lblAuthenticationMode.Text = section.Mode.ToString();

}

catch (Exception ex)

{

lblAuthenticationMode.Text = ex.Message;

}

</script>

<title>Show Config Remote</title>

</head>

<body>

<div>

<asp:Label

id=”lblServer”

Text=”Server:”

AssociatedControlID=”txtServer”

Runat=”server” />

<br />

<asp:TextBox

id=”txtServer”

<asp:Label

id=”lblUserName”

Text=”User Name:”

AssociatedControlID=”txtUserName”

<br />

<asp:TextBox

id=”txtUserName”

<asp:Label

id=”lblPassword”

Text=”Password:”

AssociatedControlID=”txtPassword”

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<br />

<asp:TextBox

id=”txtPassword”

TextMode=”Password”

<asp:Button

id=”btnSubmit”

Text=”Submit”

OnClick=”btnSubmit_Click”

<hr />

Authentication Mode:

<asp:Label

id=”lblAuthenticationMode”

</div>

</form>

</body>

</html>

You can use the page in Listing 34.13 even when the web server is located in some distant

part of the Internet You can enter a domain name or IP address in the server field

Using the Configuration Class

When you use one of the WebConfigurationManager Open methods—such as the

OpenMachineConfiguration() or OpenWebConfiguration() methods—the method returns

an instance of the Configuration class This class supports the following properties:

AppSettings—Returns the appSettings configuration section

ConnectionStrings—Returns the connectionStrings configuration section

EvaluationContext—Returns an instance of the ContextInformation class that

enables you to determine the context of the configuration information

FilePath—Returns the physical file path to the configuration file

HasFile—Returns True when there is a file that corresponds to the configuration

information

Locations—Returns a list of locations defined by the configuration

NamespaceDeclared—Returns True when the configuration file includes a namespace

declaration

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RootSectionGroup—Returns the root section group

SectionGroups—Returns the child section groups contained by this configuration

Sections—Returns the child sections contained by this configuration

The Configuration class also supports the following methods:

GetSection—Enables you to return the specified configuration section

GetSectionGroup—Enables you to return the specified configuration section group

Save—Enables you to save any configuration changes

SaveAs—Enables you to save the configuration as a new file

A configuration file contains two basic types of entities: section groups and sections For

example, the <system.web> element in a configuration file represents a section group The

<system.web> section group contains child sections such as the <authentication> and

<httpRuntime> sections

You can use the Configuration.RootSectionGroup property to get the primary section

group in a configuration file You can use the SectionGroups property to return all of a

section group’s child section groups and the Sections property to return all of a section

group’s child sections

For example, the page in Listing 34.14 recursively displays the contents of the

Machine.config file in a TreeView control (see Figure 34.9)

FIGURE 34.9 Displaying all configuration sections from the system.web configuration section

group

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LISTING 34.14 ShowConfigContents.aspx

void Page_Load()

{

// Add first node

TreeNode parentNode = new TreeNode(“configuration”);

TreeView1.Nodes.Add(parentNode);

// Start from the root section group

Configuration config = WebConfigurationManager.OpenMachineConfiguration();

// Show child section groups

AddChildSectionGroups(parentNode, config.RootSectionGroup);

// Show child sections

AddChildSections(parentNode, config.RootSectionGroup);

}

private void AddChildSectionGroups(TreeNode parentNode, ConfigurationSectionGroup

parentConfigSectionGroup)

{

foreach (ConfigurationSectionGroup configSectionGroup

➥in parentConfigSectionGroup.SectionGroups)

{

TreeNode childNode = new TreeNode(configSectionGroup.SectionGroupName);

parentNode.ChildNodes.Add(childNode);

AddChildSectionGroups(childNode, configSectionGroup);

AddChildSections(childNode, configSectionGroup);

}

private void AddChildSections(TreeNode parentNode, ConfigurationSectionGroup

parentConfigSectionGroup)

{

foreach (ConfigurationSection configSection in

parentConfigSectionGroup.Sections)

{

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TreeNode childNode = new

TreeNode(configSection.SectionInformation.Name);

parentNode.ChildNodes.Add(childNode);

}

</script>

<title>Show Config Contents</title>

</head>

<body>

<div>

<asp:TreeView

id=”TreeView1”

</div>

</form>

</body>

</html>

Modifying Configuration Sections

You can use the WebConfigurationManager class not only when opening a configuration

file to read the values of various configuration settings, but you also can use the

WebConfigurationManager class to modify existing configuration settings or add new

ones

The Configuration class supports two methods for saving configuration information: the

Save() and SaveAs() methods For example, the page in Listing 34.15 enables you to turn

on and off debugging for an application (see Figure 34.10)

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LISTING 34.15 ShowConfigModify.aspx

void Page_Load()

{

if (!Page.IsPostBack)

{

Configuration config =

WebConfigurationManager.OpenWebConfiguration(Request.ApplicationPath);

CompilationSection section =

(CompilationSection)config.GetSection(“system.web/compilation”);

chkDebug.Checked = section.Debug;

}

protected void btnUpdate_Click(object sender, EventArgs e)

{

FIGURE 34.10 Modifying the value of the Debug configuration setting

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Configuration config =

WebConfigurationManager.OpenWebConfiguration(Request.ApplicationPath);

CompilationSection section =

(CompilationSection)config.GetSection(“system.web/compilation”);

section.Debug = chkDebug.Checked;

config.Save(ConfigurationSaveMode.Modified);

}

</script>

<title>Show Config Modify</title>

</head>

<body>

<div>

<asp:CheckBox

id=”chkDebug”

Text=”Enable Debugging?”

<asp:Button

id=”btnUpdate”

Text=”Update”

OnClick=”btnUpdate_Click”

</div>

</form>

</body>

</html>

The page in Listing 34.15 loads the application root Web.config file with the help of the

OpenWebConfiguration() method (The Nothing parameter causes the root Web.config file

to be loaded.) Next, the value of the Compilation.Debug property is modified Finally, the

Save() method is called to save this change

When you call the Save() method, you can pass a ConfigurationSaveMode parameter to

the method This parameter can have the following values:

Full—Saves all configuration settings, regardless of whether they have been

modified

Minimal—Saves only those configuration settings that are different from their

inherited value

Modified—Saves only those configuration settings that have been modified

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To use the Save() or SaveAs() methods, the account associated with the page must have

Write permissions for the folder in which the configuration file is saved By default, when

pages are served from Internet Information Server, ASP.NET pages execute in the security

context of the NETWORK SERVICE account (for Windows Server 2003) or the ASPNET

account (for other operating systems) By default, neither of these accounts have

permis-sions to save configuration changes

NOTE

To make things more confusing, when pages are served from the web server included

with Visual Web Developer, the pages are always served in the security context of the

current user

There are multiple ways that you can get around this permission problem First, remember

that you can use many of the methods of the WebConfigurationManager class from a

console application or a Windows Forms application If you build this type of application,

you can sidestep these security issues

Another option is to enable per-request impersonation for your ASP.NET application

When impersonation is enabled, an ASP.NET page executes within the security context of

the user making the page request If the user account has permissions to write to the file

system, the page has permissions to write to the file system

The web configuration file in Listing 34.16 enables impersonation

LISTING 34.16 Web.config

<?xml version=”1.0”?>

<system.web>

</system.web>

</configuration>

If you add the configuration file in Listing 34.16 to the same folder that contains the file

in Listing 34.15, you can make modifications to configuration files

WARNING

Most changes to a configuration file result in an application restart When an ASP.NET

application restarts, all data stored in memory is blown away For example, all data

cached in the Cache object or Session state is lost Also keep in mind that allowing

remote configuration changes on a production server can result in a big security hole,

so this type of arrangement is only advisable for development and testing environments

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Provisioning a New Website

When you provision new websites, you often need to create a new virtual directory The

Configuration API doesn’t provide you with any help here; however, you can create new

virtual directories (and applications) by taking advantage of the classes in the

System.DirectoryServices namespace These classes enable you to use Active Directory

Services Interface (ADSI) to modify properties of Internet Information Server

NOTE

You can also manipulate Internet Information Server properties by using Windows

Management Instrumentation (WMI) For more information, see the topic “Using WMI to

Configure IIS” at the Microsoft MSDN website (msdn.microsoft.com)

Before you can use the classes from the System.DirectoryServices namespace, you need

to add a reference to the System.DirectoryServices.dll assembly In Visual Web

Developer, select Website, Add Reference, and select System.DirectoryServices.dll

For example, the page in Listing 34.17 enables you to provision a new ASP.NET

applica-tion (see Figure 34.11) The page creates a new virtual directory and a new applicaapplica-tion

The page also creates a new web configuration file in the virtual directory that contains

the default language and debug settings you specify

FIGURE 34.11 Creating a new ASP.NET application

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