Uri

URI stands for Universal Resource Identifier. We can use the Uri class in the C# programming language to represents URIs. This helps for strings starting with "http."

Class info

In C# programs, you can manage URI data directly with strings. But IndexOf and Substring often involve bugs and errors. The Uri class simplifies this problem.

Uri example

We show the properties you can access on the Uri instance. First we must create a Uri instance using the Uri constructor (new Uri).

using System;

Uri uri = new Uri("https://www.dotnetperls.com/");

// Print properties of Uri instance.
Console.WriteLine("AbsolutePath = {0}", uri.AbsolutePath);
Console.WriteLine("AbsoluteUri = {0}", uri.AbsoluteUri);
Console.WriteLine("Authority = {0}", uri.Authority);
Console.WriteLine("DnsSafeHost = {0}", uri.DnsSafeHost);
Console.WriteLine("Fragment = {0}", uri.Fragment);
Console.WriteLine("Host = {0}", uri.Host);
Console.WriteLine("HostNameType = {0}", uri.HostNameType);
Console.WriteLine("IsAbsoluteUri = {0}", uri.IsAbsoluteUri);
Console.WriteLine("IsDefaultPort = {0}", uri.IsDefaultPort);
Console.WriteLine("IsFile = {0}", uri.IsFile);
Console.WriteLine("IsLoopback = {0}", uri.IsLoopback);
Console.WriteLine("IsUnc = {0}", uri.IsUnc);
Console.WriteLine("LocalPath = {0}", uri.LocalPath);
Console.WriteLine("OriginalString = {0}", uri.OriginalString);
Console.WriteLine("PathAndQuery = {0}", uri.PathAndQuery);
Console.WriteLine("Port = {0}", uri.Port);
Console.WriteLine("Query = {0}", uri.Query);
Console.WriteLine("Scheme = {0}", uri.Scheme);
Console.WriteLine("Segments = {0}", string.Join(",", uri.Segments));
Console.WriteLine("UserEscaped = {0}", uri.UserEscaped);
Console.WriteLine("UserInfo = {0}", uri.UserInfo);
AbsolutePath = /
AbsoluteUri = https://www.dotnetperls.com/
Authority = www.dotnetperls.com
DnsSafeHost = www.dotnetperls.com
Fragment =
Host = www.dotnetperls.com
HostNameType = Dns
IsAbsoluteUri = True
IsDefaultPort = True
IsFile = False
IsLoopback = False
IsUnc = False
LocalPath = /
OriginalString = https://www.dotnetperls.com/
PathAndQuery = /
Port = 443
Query =
Scheme = https
Segments = /
UserEscaped = False
UserInfo =

IsBaseOf

One useful method on the Uri class instance is the IsBaseOf method. This method lets you determine if one Uri is contained at the start of the second Uri.

using System;

// Two example Uri instances.
Uri uri1 = new Uri("http://dotnetperls.com/");
Uri uri2 = new Uri("http://dotnetperls.com/test/");
if (uri1.IsBaseOf(uri2))
{
    Console.WriteLine(true); // Written.
}
if (uri2.IsBaseOf(uri1))
{
    Console.WriteLine(false); // Not written.
}
True

GetLeftPart

Left parts include the scheme, the URI authority, the full path, and the full path and the query string. The argument UriPartial.Scheme will return the scheme "http://".

using System;

// An example Uri instance.
Uri uri = new Uri("http://dotnetperls.com/test/?cat=1");

// Test the GetLeftPart method.
Console.WriteLine(uri.GetLeftPart(UriPartial.Authority));
Console.WriteLine(uri.GetLeftPart(UriPartial.Path));
Console.WriteLine(uri.GetLeftPart(UriPartial.Query));
Console.WriteLine(uri.GetLeftPart(UriPartial.Scheme));
http://dotnetperls.com
http://dotnetperls.com/test/
http://dotnetperls.com/test/?cat=1
http://

MakeRelativeUri

We often go from a more deeply nested directory to a higher level directory. MakeRelativeUri returns a relative path to indicate traversal.

using System;

// Two absolute Uri instances.
Uri uri1 = new Uri("http://dotnetperls.com/");
Uri uri2 = new Uri("http://dotnetperls.com/Sort/Test.html");

// Get relative paths between them in both directions.
Console.WriteLine("uri2 to uri1 = {0}", uri2.MakeRelativeUri(uri1));
Console.WriteLine("uri1 to uri2 = {0}", uri1.MakeRelativeUri(uri2));
uri2 to uri1 = ../
uri1 to uri2 = Sort/Test.html

Scheme string

This program prints out the values of all the scheme strings that are found on the Uri type in the .NET Framework. You can see that the standard scheme delimiter is "://".

using System;

// Print out the scheme delimiter.
// ... Then print out the various schemes.
Console.WriteLine(Uri.SchemeDelimiter);
Console.WriteLine(Uri.UriSchemeFile);
Console.WriteLine(Uri.UriSchemeFtp);
Console.WriteLine(Uri.UriSchemeGopher);
Console.WriteLine(Uri.UriSchemeHttp);
Console.WriteLine(Uri.UriSchemeHttps);
Console.WriteLine(Uri.UriSchemeMailto);
Console.WriteLine(Uri.UriSchemeNetPipe);
Console.WriteLine(Uri.UriSchemeNetTcp);
Console.WriteLine(Uri.UriSchemeNews);
Console.WriteLine(Uri.UriSchemeNntp);
://
file
ftp
gopher
http
https
mailto
net.pipe
net.tcp
news
nntp

CheckHostName

We test CheckHostName and CheckSchemeName. These methods serve as parsing validation routines, in that they verify the syntax of the argument.

using System;

// Use CheckHostName and CheckSchemeName methods.
Console.WriteLine(Uri.CheckHostName("dotnetperls.com"));
Console.WriteLine(Uri.CheckSchemeName("http"));
Console.WriteLine(Uri.CheckSchemeName(":)"));
Dns
True
False

TryCreate

This method uses the tester-doer pattern to construct Uri objects. This is ideal if you do not know if the string you are using is a valid URI.

using System;

Uri uri1;
if (Uri.TryCreate("http://dotnetperls.com/", UriKind.Absolute, out uri1))
{
    Console.WriteLine("1 = {0}", uri1); // Reached.
}
Uri uri2;
if (Uri.TryCreate("http:dotnetperls-com", UriKind.Absolute, out uri2))
{
    Console.WriteLine("2 = {0}", uri2); // Not reached.
}
1 = http://dotnetperls.com/

Hex

The Uri type also provides some helper methods for hexadecimal characters and strings. Hexadecimal is an alternative representation of values.

using System;

// Use hex methods.
int value = Uri.FromHex('A');
string escape = Uri.HexEscape(' ');
bool hex = Uri.IsHexDigit('A');

// Print.
Console.WriteLine(value);
Console.WriteLine(escape);
Console.WriteLine(hex);
10
%20
True

IsWellFormedUriString

How can you determine if you have a well-formed URI if it is represented as a string? You can use the IsWellFormedUriString method on the Uri type.

using System;

// Use IsWellFormedUriString method.
bool a = Uri.IsWellFormedUriString("http://dotnetperls.com/test", UriKind.Absolute);
bool b = Uri.IsWellFormedUriString("http:testcom-net", UriKind.Absolute);

// Display bools.
Console.WriteLine(a);
Console.WriteLine(b);
True
False

UriBuilder

This creates URIs from their individual parts. It handles every URI part, including the host name, path and port. It is useful in code that involves URI creation.

using System;

// Use UriBuilder constructor.
UriBuilder u1 = new UriBuilder("http", "www.dotnetperls.com");
Console.WriteLine(u1.ToString());

// Use UriBuilder properties.
UriBuilder u2 = new UriBuilder();
u2.Host = "www.dotnetperls.com";
u2.Path = "uribuilder";
u2.Scheme = "http"; // Same as "http://"
Console.WriteLine(u2.ToString());

// Convert to Uri.
Uri uri = u2.Uri;
http://www.dotnetperls.com/
http://www.dotnetperls.com/uribuilder

Notes, UriBuilder

We find some interesting behavior with the UriBuilder. The Scheme can be set to "http" or "http://" and it will have the same result.

Summary

The Uri class, part of the System namespace, provides a powerful abstraction for simplifying and unifying URI manipulations and selections. It has many methods and properties.