System.Uri Class

Provides an object representation of a uniform resource identifier (URI) and easy access to the parts of the URI.

See Also: Uri

Syntax

[System.ComponentModel.TypeConverter(typeof(System.UriTypeConverter))]
public class Uri : ISerializable

Remarks

A URI is a compact representation of a resource available to your application on the intranet or Internet. The Uri class defines the properties and methods for handling URIs, including parsing, comparing, and combining. The Uri class properties are read-only; to create a modifiable object, use the UriBuilder class.

Relative URIs (for example, "/new/index.htm") must be expanded with respect to a base URI so that they are absolute. The Uri.MakeRelative(Uri) method is provided to convert absolute URIs to relative URIs when necessary.

The Uri constructors do not escape URI strings if the string is a well-formed URI including a scheme identifier.

The Uri properties return a canonical data representation in escaped encoding, with all characters with Unicode values greater than 127 replaced with their hexadecimal equivalents. To put the URI in canonical form, the Uri constructor performs the following steps:

  • Converts the URI scheme to lowercase.

  • Converts the host name to lowercase.

  • If the host name is an IPv6 address, the canonical IPv6 address is used. ScopeId and other optional IPv6 data are removed.

  • Removes default and empty port numbers.

  • Canonicalizes the path for hierarchical URIs by compacting sequences such as /./, /../, //, including escaped representations. Note that there are some schemes for which escaped representations are not compacted.

  • For hierarchical URIs, if the host is not terminated with a forward slash (/), one is added.

  • By default, any reserved characters in the URI are escaped in accordance with RFC 2396. This behavior changes if International Resource Identifiers or International Domain Name parsing is enabled in which case reserved characters in the URI are escaped in accordance with RFC 3986 and RFC 3987.

As part of canonicalization in the constructor for some schemes, escaped representations are compacted. The schemes for which URI will compact escaped sequences include the following: file, http, https, net.pipe, and net.tcp. For all other schemes, escaped sequences are not compacted. For example: if you percent encode the two dots ".." as "%2E%2E" then the URI constructor will compact this sequence for some schemes. For example, the following code sample shows a URI constructor for the http scheme.

Example

    Uri uri = new Uri("http://myUrl/%2E%2E/%2E%2E");
    Console.WriteLine(uri.AbsoluteUri);
    Console.WriteLine(uri.PathAndQuery);

When this code is executed, it returns the following output with the escaped sequence compacted.

Example

http://myUrl/
/

The following code example shows a URI constructor for the ftp scheme:

Example

    Uri uri = new Uri("ftp://myUrl/%2E%2E/%2E%2E");
    Console.WriteLine(uri.AbsoluteUri);
    Console.WriteLine(uri.PathAndQuery);

When this code is executed, it returns the following output with the escaped sequence not compacted.

Example

ftp://myUrl/%2E%2E/%2E%2E
/%2E%2E/%2E%2E

You can transform the contents of the Uri class from an escape encoded URI reference to a readable URI reference by using the Uri.ToString method. Note that some reserved characters might still be escaped in the output of the Uri.ToString method. This is to support unambiguous reconstruction of a URI from the value returned by Uri.ToString.

Some URIs include a fragment identifier or a query or both. A fragment identifier is any text that follows a number sign (#), not including the number sign; the fragment text is stored in the Uri.Fragment property. Query information is any text that follows a question mark (?) in the URI; the query text is stored in the Uri.Query property.

In the .NET Framework version 1.1, if the string specified to a constructor contains an unknown scheme and "c:\", the Uri class inserts "//" after the colon. For example, the URI xyz:c:\abc is converted to xyz://c:/abc. In the .NET Framework version 2.0, this behavior has been removed, and the example string is converted to xyz:c:/abc.

Note:

The URI class supports the use of IP addresses in both quad-notation for IPv4 protocol and colon-hexadecimal for IPv6 protocol. Remember to enclose the IPv6 address in square brackets, as in http://[::1].

International Resource Identifier Support

Web addresses are typically expressed using uniform resource identifiers that consist of a very restricted set of characters:

  • Upper and lower case ASCII letters from the English alphabet.

  • Digits from 0 to 9.

  • A small number of other ASCII symbols.

The specifications for URIs are documented in RFC 2396, RFC 2732, RFC 3986, and RFC 3987 published by the Internet Engineering Task Force (IETF).

With the growth of the Internet, there is a growing need to identify resources using languages other than English. Identifiers which facilitate this need and allow non-ASCII characters (characters in the Unicode/ISO 10646 character set) are known as International Resource Identifiers (IRIs). The specifications for IRIs are documented in RFC 3987 published by IETF. Using IRIs allows a URL to contain Unicode characters.

The existing Uri class has been extended in .NET Framework v3.5, 3.0 SP1, and 2.0 SP1 to provide IRI support based on RFC 3987. Current users will not see any change from the .NET Framework 2.0 behavior unless they specifically enable IRI. This ensures application compatibility with prior versions of the .NET Framework.

To enable support for IRI, the following change is required:

  • Specify whether you want Internationalized Domain Name (IDN) parsing applied to the domain name and whether IRI parsing rules should be applied. This can be done in the machine.config or in the app.config file. For example, add the following:

Enabling IDN will convert all Unicode labels in a domain name to their Punycode equivalents. Punycode names contain only ASCII characters and always start with the xn-- prefix. The reason for this is to support existing DNS servers on the Internet, since most DNS servers only support ASCII characters (see RFC 3940).

Enabling IRI and IDN affects the value of the Uri.DnsSafeHost property. Enabling IRI and IDN can also change the behavior of the Uri.Equals(Object), Uri.OriginalString, Uri.GetComponents(UriComponents,UriFormat), and Uri.IsWellFormedOriginalString methods.

There are three possible values for IDN depending on the DNS servers that are used:

  • idn enabled = All

    This value will convert any Unicode domain names to their Punycode equivalents (IDN names).

  • idn enabled = AllExceptIntranet

    This value will convert all Unicode domain names not on the local Intranet to use the Punycode equivalents (IDN names). In this case to handle international names on the local Intranet, the DNS servers that are used for the Intranet should support Unicode name resolution.

  • idn enabled = None

    This value will not convert any Unicode domain names to use Punycode. This is the default value which is consistent with the .NET Framework 2.0 behaviour.

Enabling IRI parsing (iriParsing enabled = true) will do normalization and character checking according to the latest IRI rules in RFC 3986 and RFC 3987. The default value is false and will do normalization and character checking according to RFC 2396 and RFC 2732 (for IPv6 literals).

IRI and IDN processing in the Uri class can also be controlled using the IriParsingElement, IdnElement, and UriSection configuration setting classes. The IriParsingElement setting enables or disables IRI processing in the Uri class. The IdnElement setting enables or disables IDN processing in the Uri class. The IriParsingElement setting also indirectly controls IDN. IRI processing must be enabled for IDN processing to be possible. If IRI processing is disabled, then IDN processing will be set to the default setting where the .NET Framework 2.0 behavior is used for compatibility and IDN names are not used.

The configuration setting for the IriParsingElement and IdnElement will be read once when the first Uri class is constructed. Changes to configuration settings after that time are ignored.

The GenericUriParser class has also been extended to allow creating a customizable parser that supports IRI and IDN. The behavior of a GenericUriParser object is specified by passing a bitwise combination of the values available in the GenericUriParserOptions enumeration to the GenericUriParser constructor. The GenericUriParserOptions.IriParsing type indicates the parser supports the parsing rules specified in RFC 3987 for International Resource Identifiers (IRI). Whether IRI is used is dictated by the configuration values previously discussed.

The GenericUriParserOptions.Idn type indicates the parser supports Internationalized Domain Name (IDN) parsing (IDN) of host names. Whether IDN is used is dictated by the configuration values previously discussed.

Performance Considerations

If you use a Web.config file that contains URIs to initialize your application, additional time is required to process the URIs if their scheme identifiers are nonstandard. In such a case, initialize the affected parts of your application when the URIs are needed, not at start time.

Starting with Mono 3.10, Mono adopted the International Resource Identifier ("IRI") for parsing urls, just like .NET 4.5 does (https://msdn.microsoft.com/en-us/library/bb968786%28v=vs.110%29.aspx).

It is possible to disable IRI-based parsing by setting the MONO_URI_IRIPARSING environment variable to the string "false"

To help compatibility with third party software that disabled this behavior, we used the same internal field to turn this feature on or off by poking at the Uri internals.

c# Example

FieldInfo iriParsingField = typeof (Uri).GetField ("s_IriParsing",
    BindingFlags.Static | BindingFlags.GetField | BindingFlags.NonPublic);
if (iriParsingField != null)
    iriParsingField.SetValue (null, false);

Thread Safety

All public static members of this type are safe for multithreaded operations. No instance members are guaranteed to be thread safe.

Requirements

Namespace: System
Assembly: System (in System.dll)
Assembly Versions: 1.0.x.x, 1.0.5000.0, 2.0.0.0, 4.0.0.0

The members of System.Uri are listed below.

See Also: Object

Public Constructors

Initializes a new instance of the Uri class with the specified URI.

Initializes a new instance of the Uri class with the specified URI, with explicit control of character escaping.

Initializes a new instance of the Uri class with the specified URI. This constructor allows you to specify if the URI string is a relative URI, absolute URI, or is indeterminate.

Initializes a new instance of the Uri class based on the specified base URI and relative URI string.

Initializes a new instance of the Uri class based on the combination of a specified base Uri instance and a relative Uri instance.

Initializes a new instance of the Uri class based on the specified base and relative URIs, with explicit control of character escaping.

Protected Constructors

Initializes a new instance of the Uri class from the specified instances of the SerializationInfo and StreamingContext classes.

Public Fields

static readonly
SchemeDelimiterString.

Specifies the characters that separate the communication protocol scheme from the address portion of the URI. This field is read-only.

static readonly
UriSchemeFileString (file).

Specifies that the URI is a pointer to a file. This field is read-only.

static readonly
UriSchemeFtpString (ftp).

Specifies that the URI is accessed through the File Transfer Protocol (FTP). This field is read-only.

static readonly
UriSchemeGopherString (gopher).

Specifies that the URI is accessed through the Gopher protocol. This field is read-only.

static readonly
UriSchemeHttpString (http).

Specifies that the URI is accessed through the Hypertext Transfer Protocol (HTTP). This field is read-only.

static readonly
UriSchemeHttpsString (https).

Specifies that the URI is accessed through the Secure Hypertext Transfer Protocol (HTTPS). This field is read-only.

static readonly
UriSchemeMailtoString (mailto).

Specifies that the URI is an e-mail address and is accessed through the Simple Mail Transport Protocol (SMTP). This field is read-only.

static readonly
UriSchemeNetPipeString.

Specifies that the URI is accessed through the NetPipe scheme used by Windows Communication Foundation (WCF). This field is read-only.

static readonly
UriSchemeNetTcpString.

Specifies that the URI is accessed through the NetTcp scheme used by Windows Communication Foundation (WCF). This field is read-only.

static readonly
UriSchemeNewsString (news).

Specifies that the URI is an Internet news group and is accessed through the Network News Transport Protocol (NNTP). This field is read-only.

static readonly
UriSchemeNntpString (nntp).

Specifies that the URI is an Internet news group and is accessed through the Network News Transport Protocol (NNTP). This field is read-only.

Public Properties

[read-only]
AbsolutePathString.

Gets the absolute path of the URI.

[read-only]
AbsoluteUriString.

Gets the absolute URI.

[read-only]
AuthorityString.

Gets the Domain Name System (DNS) host name or IP address and the port number for a server.

[read-only]
DnsSafeHostString.

Gets an unescaped host name that is safe to use for DNS resolution.

[read-only]
FragmentString.

Gets the escaped URI fragment.

[read-only]
HostString.

Gets the host component of this instance.

[read-only]
HostNameTypeUriHostNameType.

Gets the type of the host name specified in the URI.

[read-only]
IsAbsoluteUriBoolean.

Gets whether the Uri instance is absolute.

[read-only]
IsDefaultPortBoolean.

Gets whether the port value of the URI is the default for this scheme.

[read-only]
IsFileBoolean.

Gets a value indicating whether the specified Uri is a file URI.

[read-only]
IsLoopbackBoolean.

Gets whether the specified Uri references the local host.

[read-only]
IsUncBoolean.

Gets whether the specified Uri is a universal naming convention (UNC) path.

[read-only]
LocalPathString.

Gets a local operating-system representation of a file name.

[read-only]
OriginalStringString.

Gets the original URI string that was passed to the Uri constructor.

[read-only]
PathAndQueryString.

Gets the Uri.AbsolutePath and Uri.Query properties separated by a question mark (?).

[read-only]
PortInt32.

Gets the port number of this URI.

[read-only]
QueryString.

Gets any query information included in the specified URI.

[read-only]
SchemeString.

Gets the scheme name for this URI.

[read-only]
SegmentsString[].

Gets an array containing the path segments that make up the specified URI.

[read-only]
UserEscapedBoolean.

Indicates that the URI string was completely escaped before the Uri instance was created.

[read-only]
UserInfoString.

Gets the user name, password, or other user-specific information associated with the specified URI.

Public Methods

static
CheckHostName(String) : UriHostNameType

Determines whether the specified host name is a valid DNS name.

static
CheckSchemeName(String) : Boolean

Determines whether the specified scheme name is valid.

static
Compare(Uri, Uri, UriComponents, UriFormat, StringComparison) : Int32

Compares the specified parts of two URIs using the specified comparison rules.

override
Equals(Object) : Boolean

Compares two Uri instances for equality.

static
EscapeDataString(String) : String

Converts a string to its escaped representation.

static
EscapeUriString(String) : String

Converts a URI string to its escaped representation.

static
FromHex(Char) : Int32

Gets the decimal value of a hexadecimal digit.

GetComponents(UriComponents, UriFormat) : String

Gets the specified components of the current instance using the specified escaping for special characters.

override
GetHashCode() : Int32

Gets the hash code for the URI.

GetLeftPart(UriPartial) : String

Gets the specified portion of a Uri instance.

static
HexEscape(Char) : String

Converts a specified character into its hexadecimal equivalent.

static
HexUnescape(String, ref Int32) : Char
Converts a specified escaped hexadecimal representation of a character to the character.
IsBaseOf(Uri) : Boolean

Determines whether the current Uri instance is a base of the specified Uri instance.

static
IsHexDigit(Char) : Boolean

Determines whether a specified character is a valid hexadecimal digit.

static
IsHexEncoding(String, Int32) : Boolean

Determines whether a character in a string is hexadecimal encoded.

IsWellFormedOriginalString() : Boolean

Indicates whether the string used to construct this Uri was well-formed and is not required to be further escaped.

static
IsWellFormedUriString(String, UriKind) : Boolean

Indicates whether the string is well-formed by attempting to construct a URI with the string and ensures that the string does not require further escaping.

MakeRelative(Uri) : String

Determines the difference between two Uri instances.

MakeRelativeUri(Uri) : Uri

Determines the difference between two Uri instances.

override
ToString() : String

Gets a canonical string representation for the specified Uri instance.

static
TryCreate(String, UriKind, out Uri) : Boolean
static
TryCreate(Uri, String, out Uri) : Boolean
static
TryCreate(Uri, Uri, out Uri) : Boolean
static
UnescapeDataString(String) : String

Converts a string to its unescaped representation.

Protected Methods

Canonicalize()

Converts the internally stored URI to canonical form.

CheckSecurity()

Calling this method has no effect.

Escape()

Converts any unsafe or reserved characters in the path component to their hexadecimal character representations.

static
EscapeString(String) : String

Converts a string to its escaped representation.

GetObjectData(SerializationInfo, StreamingContext)

Returns the data needed to serialize the current instance.

IsBadFileSystemCharacter(Char) : Boolean

Gets whether a character is invalid in a file system name.

static
IsExcludedCharacter(Char) : Boolean

Gets whether the specified character should be escaped.

IsReservedCharacter(Char) : Boolean

Gets whether the specified character is a reserved character.

Parse()

Parses the URI of the current instance to ensure it contains all the parts required for a valid URI.

Unescape(String) : String

Converts the specified string by replacing any escape sequences with their unescaped representation.

Public Operators

static
Equality(Uri, Uri)

Determines whether two Uri instances have the same value.

static
Inequality(Uri, Uri)

Determines whether two Uri instances do not have the same value.

Explicitly Implemented Interface Members

Uri$ISerializable.GetObjectData(SerializationInfo,StreamingContext)

Returns the data needed to serialize the current instance.