ISAPI Filters <isapiFilters>


The <isapiFilters> element allows you to manage ISAPI filters on your Internet Information Services (IIS) 7 server. You can add an ISAPI filter when you want to enhance Web server functionality. For example, you might have an ISAPI filter that captures information about HTTP requests and saves the information to a database.

Note: Although IIS 7 supports ISAPI filters, Microsoft recommends that you extend Web server functionality by using modules instead of by using ISAPI filters.

The <isapiFilters> element can contain one or more <filter> elements, each of which defines an ISAPI filter enabled for your server or Web site. It can also contain a <remove> element, which you can use to remove a specific ISAPI filter inherited from higher in the configuration hierarchy. The <isapiFilters> element can also contain a <clear> element, which removes all ISAPI filters inherited from higher in the configuration hierarchy.


Version Notes
IIS 7.5 The <isapiFilters> element was not modified in IIS 7.5.
IIS 7.0 The <isapiFilters> element was introduced in IIS 7.0.
IIS 6.0 The <isapiFilters> element replaces the IIS 6.0 FilterEnableCache and FilterPath metabase properties.


To use the <isapiFilters> element, you must install the ISAPI Filters module on your IIS 7 server. To do so, use the following steps.

Windows Server 2008 or Windows Server 2008 R2

  1. On the taskbar, click Start, point to Administrative Tools, and then click Server Manager.
  2. In the Server Manager hierarchy pane, expand Roles, and then click Web Server (IIS).
  3. In the Web Server (IIS) pane, scroll to the Role Services section, and then click Add Role Services.
  4. On the Select Role Services page of the Add Role Services Wizard, select ISAPI Filters, and then click Next.

  5. On the Confirm Installation Selections page, click Install.
  6. On the Results page, click Close.

Windows Vista or Windows 7

  1. On the taskbar, click Start, and then click Control Panel.
  2. In Control Panel, click Programs and Features, and then click Turn Windows Features on or off.
  3. In the Windows Features dialog box, expand Internet Information Services, then World Wide Web Services, then Application Development Features.

  4. Select ISAPI Filters, and then click OK.

How To

How to add an ISAPI filter

  1. Open Internet Information Services (IIS) Manager:
    • If you are using Windows Server 2008 or Windows Server 2008 R2:
      • On the taskbar, click Start, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.
    • If you are using Windows Vista or Windows 7:
      • On the taskbar, click Start, and then click Control Panel.
      • Double-click Administrative Tools, and then double-click Internet Information Services (IIS) Manager.
  2. In the Connections pane, go to the connection or site for which you want to configure ISAPI filters.
  3. In the Home pane, double-click ISAPI Filters.

  4. In the Actions pane, click Add...
  5. In the Filter name text box of the Add ISAPI Filter dialog box, type a friendly name for the ISAPI filter.
  6. In the Executable box, type the file system path of the location of ISAPI filter file or click the ellipsis (...) to navigate to the folder that contains the ISAPI filter file, and then click OK.


You can add an ISAPI filter at the server level and the site level. If you add the ISAPI filter at the server level, the filter intercepts all requests made to the server. If you add the ISAPI filter to a specific site, the filter intercepts all requests made to that site.

You can configure the <isapiFilters> element at the server level in the ApplicationHost.config file or at the site level in the appropriate Web.config file.



Child Elements

Element Description
clear Optional element.

Removes all references to ISAPI filters from the ISAPI filters collection.
filter Optional element.

Adds an ISAPI filter to the ISAPI filters collection.
remove Optional element.

Removes a reference to an ISAPI filter from the ISAPI filters collection.

Configuration Sample

The following configuration example adds an ISAPI filter named SalesQueryIsapi to a Web site or application. The sample names and enables the ISAPI filter with the name and enabled attributes. It also uses the enableCache attribute to disable HTTP.sys caching and the path attribute to specify the location of the ISAPI DLL.

            path="C:\Inetpub\filters\SalesFilter.dll" />

Sample Code

The following examples configure an ISAPI filter named SalesQueryIsapi on the server. Each of the examples use the name property to specify a name for the ISAPI filter, the enableCache property to disable HTTP.sys caching, and the path property to specify the location of the ISAPI DLL.


appcmd.exe set config -section:system.webServer/isapiFilters /+"[name='SalesQueryIsapi',path='c:\Inetpub\\filters\SalesQueryIsapi.dll',enabled='True',enableCache='True']" /commit:apphost

Note: You must be sure to set the commit parameter to apphost when you use AppCmd.exe to configure these settings. This commits the configuration settings to the appropriate location section in the ApplicationHost.config file.


using System;
using System.Text;
using Microsoft.Web.Administration;

internal static class Sample
   private static void Main()
      using (ServerManager serverManager = new ServerManager())
         Configuration config = serverManager.GetApplicationHostConfiguration();
         ConfigurationSection isapiFiltersSection = config.GetSection("system.webServer/isapiFilters");
         ConfigurationElementCollection isapiFiltersCollection = isapiFiltersSection.GetCollection();

         ConfigurationElement filterElement = isapiFiltersCollection.CreateElement("filter");
         filterElement["name"] = @"SalesQueryIsapi";
         filterElement["path"] = @"c:\Inetpub\\filters\SalesQueryIsapi.dll";
         filterElement["enabled"] = true;
         filterElement["enableCache"] = true;



Imports System
Imports System.Text
Imports Microsoft.Web.Administration

Module Sample
   Sub Main()
      Dim serverManager As ServerManager = New ServerManager
      Dim config As Configuration = serverManager.GetApplicationHostConfiguration
      Dim isapiFiltersSection As ConfigurationSection = config.GetSection("system.webServer/isapiFilters")
      Dim isapiFiltersCollection As ConfigurationElementCollection = isapiFiltersSection.GetCollection
      Dim filterElement As ConfigurationElement = isapiFiltersCollection.CreateElement("filter")
      filterElement("name") = "SalesQueryIsapi"
      filterElement("path") = "c:\Inetpub\\filters\SalesQueryIsapi.dll"
      filterElement("enabled") = True
      filterElement("enableCache") = True
   End Sub
End Module


var adminManager = new ActiveXObject('Microsoft.ApplicationHost.WritableAdminManager');
adminManager.CommitPath = "MACHINE/WEBROOT/APPHOST";
var isapiFiltersSection = adminManager.GetAdminSection("system.webServer/isapiFilters", "MACHINE/WEBROOT/APPHOST");
var isapiFiltersCollection = isapiFiltersSection.Collection;

var filterElement = isapiFiltersCollection.CreateNewElement("filter");
filterElement.Properties.Item("name").Value = "SalesQueryIsapi";
filterElement.Properties.Item("path").Value = "c:\\Inetpub\\\\filters\\SalesQueryIsapi.dll";
filterElement.Properties.Item("enabled").Value = true;
filterElement.Properties.Item("enableCache").Value = true;



Set adminManager = createObject("Microsoft.ApplicationHost.WritableAdminManager")
adminManager.CommitPath = "MACHINE/WEBROOT/APPHOST"
Set isapiFiltersSection = adminManager.GetAdminSection("system.webServer/isapiFilters", "MACHINE/WEBROOT/APPHOST")
Set isapiFiltersCollection = isapiFiltersSection.Collection

Set filterElement = isapiFiltersCollection.CreateNewElement("filter")
filterElement.Properties.Item("name").Value = "SalesQueryIsapi"
filterElement.Properties.Item("path").Value = "c:\\Inetpub\\\\filters\\SalesQueryIsapi.dll"
filterElement.Properties.Item("enabled").Value = True
filterElement.Properties.Item("enableCache").Value = True
isapiFiltersCollection.AddElement filterElement

Deprecated Elements