Provides an object representation of a uniform resource identifier (URI) and easy access to the parts of the URI.
Assembly: System (in System.dll)
Thetype exposes the following members.
|Uri(String)||Initializes a new instance of the class with the specified URI.|
|Uri(SerializationInfo, StreamingContext)||Initializes a new instance of the class from the specified instances of the SerializationInfo and StreamingContext classes.|
|Uri(String, Boolean)||Obsolete. Initializes a new instance of the class with the specified URI, with explicit control of character escaping.|
|Uri(String, UriKind)||Initializes a new instance of the class with the specified URI. This constructor allows you to specify if the URI string is a relative URI, absolute URI, or is indeterminate.|
|Uri(Uri, String)||Initializes a new instance of the class based on the specified base URI and relative URI string.|
|Uri(Uri, Uri)||Initializes a new instance of the class based on the combination of a specified base instance and a relative instance.|
|Uri(Uri, String, Boolean)||Obsolete. Initializes a new instance of the class based on the specified base and relative URIs, with explicit control of character escaping.|
|AbsolutePath||Gets the absolute path of the URI.|
|AbsoluteUri||Gets the absolute URI.|
|Authority||Gets the Domain Name System (DNS) host name or IP address and the port number for a server.|
|DnsSafeHost||Gets an unescaped host name that is safe to use for DNS resolution.|
|Fragment||Gets the escaped URI fragment.|
|Host||Gets the host component of this instance.|
|HostNameType||Gets the type of the host name specified in the URI.|
|IdnHost||The RFC 3490 compliant International Domain Name of the host, using Punycode as appropriate.|
|IsAbsoluteUri||Gets whether the instance is absolute.|
|IsDefaultPort||Gets whether the port value of the URI is the default for this scheme.|
|IsFile||Gets a value indicating whether the specified is a file URI.|
|IsLoopback||Gets whether the specified references the local host.|
|IsUnc||Gets whether the specified is a universal naming convention (UNC) path.|
|LocalPath||Gets a local operating-system representation of a file name.|
|OriginalString||Gets the original URI string that was passed to the constructor.|
|PathAndQuery||Gets the AbsolutePath and Query properties separated by a question mark (?).|
|Port||Gets the port number of this URI.|
|Query||Gets any query information included in the specified URI.|
|Scheme||Gets the scheme name for this URI.|
|Segments||Gets an array containing the path segments that make up the specified URI.|
|UserEscaped||Indicates that the URI string was completely escaped before the instance was created.|
|UserInfo||Gets the user name, password, or other user-specific information associated with the specified URI.|
|Canonicalize||Infrastructure. Obsolete. Converts the internally stored URI to canonical form.|
|CheckHostName||Determines whether the specified host name is a valid DNS name.|
|CheckSchemeName||Determines whether the specified scheme name is valid.|
|CheckSecurity||Infrastructure. Obsolete. Calling this method has no effect.|
|Compare||Compares the specified parts of two URIs using the specified comparison rules.|
|Equals||Compares two instances for equality. (Overrides Object.Equals(Object).)|
|Escape||Infrastructure. Obsolete. Converts any unsafe or reserved characters in the path component to their hexadecimal character representations.|
|EscapeDataString||Converts a string to its escaped representation.|
|EscapeString||Obsolete. Converts a string to its escaped representation.|
|EscapeUriString||Converts a URI string to its escaped representation.|
|Finalize||Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)|
|FromHex||Gets the decimal value of a hexadecimal digit.|
|GetComponents||Gets the specified components of the current instance using the specified escaping for special characters.|
|GetHashCode||Gets the hash code for the URI. (Overrides Object.GetHashCode().)|
|GetLeftPart||Gets the specified portion of a instance.|
|GetObjectData||Returns the data needed to serialize the current instance.|
|GetType||Gets the Type of the current instance. (Inherited from Object.)|
|HexEscape||Converts a specified character into its hexadecimal equivalent.|
|HexUnescape||Converts a specified hexadecimal representation of a character to the character.|
|IsBadFileSystemCharacter||Infrastructure. Obsolete. Gets whether a character is invalid in a file system name.|
|IsBaseOf||Determines whether the current instance is a base of the specified instance.|
|IsExcludedCharacter||Infrastructure. Obsolete. Gets whether the specified character should be escaped.|
|IsHexDigit||Determines whether a specified character is a valid hexadecimal digit.|
|IsHexEncoding||Determines whether a character in a string is hexadecimal encoded.|
|IsReservedCharacter||Infrastructure. Obsolete. Gets whether the specified character is a reserved character.|
|IsWellFormedOriginalString||Indicates whether the string used to construct this was well-formed and is not required to be further escaped.|
|IsWellFormedUriString||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||Obsolete. Determines the difference between two instances.|
|MakeRelativeUri||Determines the difference between two instances.|
|MemberwiseClone||Creates a shallow copy of the current Object. (Inherited from Object.)|
|Parse||Infrastructure. Obsolete. Parses the URI of the current instance to ensure it contains all the parts required for a valid URI.|
|ToString||Gets a canonical string representation for the specified instance. (Overrides Object.ToString().)|
|TryCreate(String, UriKind, Uri)||Creates a new using the specified String instance and a UriKind.|
|TryCreate(Uri, String, Uri)||Creates a new using the specified base and relative String instances.|
|TryCreate(Uri, Uri, Uri)||Creates a new using the specified base and relative instances.|
|Unescape||Infrastructure. Obsolete. Converts the specified string by replacing any escape sequences with their unescaped representation.|
|UnescapeDataString||Converts a string to its unescaped representation.|
|SchemeDelimiter||Specifies the characters that separate the communication protocol scheme from the address portion of the URI. This field is read-only.|
|UriSchemeFile||Specifies that the URI is a pointer to a file. This field is read-only.|
|UriSchemeFtp||Specifies that the URI is accessed through the File Transfer Protocol (FTP). This field is read-only.|
|UriSchemeGopher||Specifies that the URI is accessed through the Gopher protocol. This field is read-only.|
|UriSchemeHttp||Specifies that the URI is accessed through the Hypertext Transfer Protocol (HTTP). This field is read-only.|
|UriSchemeHttps||Specifies that the URI is accessed through the Secure Hypertext Transfer Protocol (HTTPS). This field is read-only.|
|UriSchemeMailto||Specifies that the URI is an e-mail address and is accessed through the Simple Mail Transport Protocol (SMTP). This field is read-only.|
|UriSchemeNetPipe||Specifies that the URI is accessed through the NetPipe scheme used by Windows Communication Foundation (WCF). This field is read-only.|
|UriSchemeNetTcp||Specifies that the URI is accessed through the NetTcp scheme used by Windows Communication Foundation (WCF). This field is read-only.|
|UriSchemeNews||Specifies that the URI is an Internet news group and is accessed through the Network News Transport Protocol (NNTP). This field is read-only.|
|UriSchemeNntp||Specifies that the URI is an Internet news group and is accessed through the Network News Transport Protocol (NNTP). This field is read-only.|
A URI is a compact representation of a resource available to your application on the intranet or Internet. The class defines the properties and methods for handling URIs, including parsing, comparing, and combining. The 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 MakeRelative method is provided to convert absolute URIs to relative URIs when necessary.
The constructors do not escape URI strings if the string is a well-formed URI including a scheme identifier.
The 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 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.
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.
The following code example shows a URI constructor for the ftp scheme:
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.
You can transform the contents of the class from an escape encoded URI reference to a readable URI reference by using the ToString method. Note that some reserved characters might still be escaped in the output of the ToString method. This is to support unambiguous reconstruction of a URI from the value returned by 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 Fragment property. Query information is any text that follows a question mark (?) in the URI; the query text is stored in the 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.
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 class has been extended in .NET Framework v3.5, 3.0 SP1, and 2.0 SP1 to provide IRI support based on RFC 3987. Users of .NET Framework versions before version 4.5 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:
<configuration> <uri> <idn enabled="All" /> <iriParsing enabled="true" /> </uri> </configuration>
Users of .NET Framework 4.5 and newer always have IRI enabled. IRI parsing cannot be changed using a .config file.
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 Equals, OriginalString, GetComponents, and 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.
When IRI parsing is enabled (iriParsing enabled = true) normalization and character checking are done according to the latest IRI rules in RFC 3986 and RFC 3987. When IRI parsing is disabled, normalization and character checking are performed according to RFC 2396 and RFC 2732 (for IPv6 literals). In versions of the .NET Framework before version 4.5, the default value is false. In .NET Framework version 4.5 and newer, the default value is true, and the enabled state of IRI parsing cannot be modified by settings in a .config file.
IRI and IDN processing in the class can also be controlled using the System.Configuration.IriParsingElement, System.Configuration.IdnElement, and System.Configuration.UriSection configuration setting classes. The System.Configuration.IriParsingElement setting enables or disables IRI processing in the class. The System.Configuration.IdnElement setting enables or disables IDN processing in the class. The System.Configuration.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 System.Configuration.IriParsingElement and System.Configuration.IdnElement will be read once when the first class is constructed. Changes to configuration settings after that time are ignored.
The System.GenericUriParser class has also been extended to allow creating a customizable parser that supports IRI and IDN. The behavior of a System.GenericUriParser object is specified by passing a bitwise combination of the values available in the System.GenericUriParserOptions enumeration to the System.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.
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.
Because of security concerns, your application should use caution when accepting instances from untrusted sources and with dontEscape set to true.You can check a URI string for validity by calling the IsWellFormedOriginalString method.