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 MakeRelativeUri 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.

• Any reserved characters in the URI are escaped in accordance with RFC 3986.

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.Query);

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

http://myUrl/
/

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.Query);

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

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 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.

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

The constructors for Uri allow a Silverlight application to create a Uri instance for many schemes as described in the Scheme property. However, only Uri instances for the UriSchemeHttp or UriSchemeHttps schemes are supported by the WebClient and HTTP classes in the System.Net namespace.

International Resource Identifier Not Supported

Performance Considerations

Because of security concerns, your application should use caution when accepting Uri instances from untrusted sources and with dontEscape set to true.

The following example creates an instance of the Uri class and uses it to create a WebRequest instance.

Dim siteUri As New Uri("http://www.contoso.com/")

Dim wr As WebRequest = WebRequest.Create(siteUri)

      Uri siteUri = new Uri("http://www.contoso.com/");

      WebRequest wr = WebRequest.Create(siteUri);

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Reference