HttpListenerElement Class

HttpListenerElement Class

.NET Framework 4.6 and 4.5

Represents the HttpListener element in the configuration file. This class cannot be inherited.

Namespace:   System.Net.Configuration
Assembly:  System (in System.dll)


public sealed class HttpListenerElement : ConfigurationElement


Initializes a new instance of the HttpListenerElement class.


Gets a reference to the top-level Configuration instance that represents the configuration hierarchy that the current ConfigurationElement instance belongs to.(Inherited from ConfigurationElement.)


Gets an ElementInformation object that contains the non-customizable information and functionality of the ConfigurationElement object. (Inherited from ConfigurationElement.)


Gets the ConfigurationElementProperty object that represents the ConfigurationElement object itself.(Inherited from ConfigurationElement.)


Gets or sets a property or attribute of this configuration element.(Inherited from ConfigurationElement.)


Gets or sets a property, attribute, or child element of this configuration element.(Inherited from ConfigurationElement.)


Gets the collection of locked attributes.(Inherited from ConfigurationElement.)


Gets the collection of locked elements.(Inherited from ConfigurationElement.)


Gets the collection of locked attributes (Inherited from ConfigurationElement.)


Gets the collection of locked elements.(Inherited from ConfigurationElement.)


Gets or sets a value indicating whether the element is locked.(Inherited from ConfigurationElement.)


Gets the collection of properties.(Inherited from ConfigurationElement.)


Gets the default timeout elements used for an HttpListener object.


Gets a value that indicates if HttpListener uses the raw unescaped URI instead of the converted URI.

System_CAPS_protmethodDeserializeElement(XmlReader, Boolean)

Reads XML from the configuration file.(Inherited from ConfigurationElement.)


Compares the current ConfigurationElement instance to the specified object.(Inherited from ConfigurationElement.)


Gets a unique value representing the current ConfigurationElement instance.(Inherited from ConfigurationElement.)


Gets the Type of the current instance.(Inherited from Object.)


Sets the ConfigurationElement object to its initial state.(Inherited from ConfigurationElement.)


Used to initialize a default set of values for the ConfigurationElement object.(Inherited from ConfigurationElement.)


Indicates whether this configuration element has been modified since it was last saved or loaded, when implemented in a derived class.(Inherited from ConfigurationElement.)


Gets a value indicating whether the ConfigurationElement object is read-only.(Inherited from ConfigurationElement.)


Resets the internal state of the ConfigurationElement object, including the locks and the properties collections.(Inherited from ConfigurationElement.)


Resets the value of the IsModified method to false when implemented in a derived class.(Inherited from ConfigurationElement.)

System_CAPS_protmethodSerializeElement(XmlWriter, Boolean)

Writes the contents of this configuration element to the configuration file when implemented in a derived class.(Inherited from ConfigurationElement.)

System_CAPS_protmethodSerializeToXmlElement(XmlWriter, String)

Writes the outer tags of this configuration element to the configuration file when implemented in a derived class.(Inherited from ConfigurationElement.)


Sets the IsReadOnly property for the ConfigurationElement object and all subelements.(Inherited from ConfigurationElement.)


Returns a string that represents the current object.(Inherited from Object.)

System_CAPS_protmethodUnmerge(ConfigurationElement, ConfigurationElement, ConfigurationSaveMode)

Modifies the ConfigurationElement object to remove all values that should not be saved. (Inherited from ConfigurationElement.)

This class corresponds to the <httpListener> Element (Network Settings) configuration element. This class provides programmatic access to information that can be stored in configuration files.

The UnescapeRequestUrl property indicates if HttpListener uses the raw unescaped URI instead of the converted URI where any percent-encoded values are converted and other normalization steps are taken.

When a HttpListener instance receives a request through the http.sys service, it creates an instance of the URI string provided by http.sys, and exposes it as the HttpListenerRequest.Url property.

The http.sys service exposes two request URI strings:

  • Raw URI

  • Converted URI

The raw URI is the System.Uri provided in the request line of a HTTP request:

GET /path/


The raw URI provided by http.sys for the request mentioned above, is "/path/". This represents the string following the HTTP verb as it was sent over the network.

The http.sys service creates a converted URI from the information provided in the request by using the URI provided in the HTTP request line and the Host header to determine the origin server the request should be forwarded to. This is done by comparing the information from the request with a set of registered URI prefixes. The HTTP Server SDK documentation refers to this converted URI as the HTTP_COOKED_URL structure.

In order to be able to compare the request with registered URI prefixes, some normalization to the request needs to be done. For the sample above the converted URI would be as follows:

The http.sys service combines the Uri.Host property value and the string in the request line to create a converted URI. In addition, http.sys and the System.Uri class also do the following:

  • Un-escapes all percent encoded values.

  • Converts percent-encoded non-ASCII characters into a UTF-16 character representation. Note that UTF-8 and ANSI/DBCS characters are supported as well as Unicode characters (Unicode encoding using the %uXXXX format).

  • Executes other normalization steps, like path compression.

Since the request doesn't contain any information about the encoding used for percent-encoded values, it may not be possible to determine the correct encoding just by parsing the percent-encoded values.

Therefore http.sys provides two registry keys for modifying the process:

Registry Key

Default Value




If zero, http.sys accepts only UTF-8-encoded URLs.

If non-zero, http.sys also accepts ANSI-encoded or DBCS-encoded URLs in requests.



If non-zero, http.sys always tries to decode a URL as UTF-8 first; if that conversion fails and EnableNonUTF8 is non-zero, Http.sys then tries to decode it as ANSI or DBCS.

If zero (and EnableNonUTF8 is non-zero), http.sys tries to decode it as ANSI or DBCS; if that is not successful, it tries a UTF-8 conversion.

When HttpListener receives a request, it uses the converted URI from http.sys as input to the Url property.

There is a need for supporting characters besides characters and numbers in URIs. An example is the following URI, which is used to retrieve customer information for customer number "1/3812":'1%2F3812')/

Note the percent-encoded slash in the Uri (%2F). This is necessary, since in this case the slash character represents data and not a path delimiter.

Passing the string to Uri constructor will lead to the following URI:'1/3812')/

Splitting the path into its segments would result in the following elements:



This is not the intent of the sender of the request.

If the UnescapeRequestUrl property is set to false, then when the HttpListener receives a request, it uses the raw URI instead of the converted URI from http.sys as input to the Url property.

.NET Framework
Available since 4.0

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Return to top
© 2015 Microsoft