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IdnMapping.GetUnicode Method (String, Int32, Int32)

Decodes a substring of one or more domain name labels encoded according to the Internationalizing Domain Names in Applications (IDNA) standard to a string of Unicode characters.

Namespace:  System.Globalization
Assembly:  mscorlib (in mscorlib.dll)

public string GetUnicode(
	string ascii,
	int index,
	int count


Type: System.String

One or more labels in the US-ASCII character range (U+0020 to U+007E) encoded according to the IDNA standard.

Type: System.Int32

A zero-based offset into ascii that specifies the start of the substring.

Type: System.Int32

The number of characters to convert in the substring that starts at the position specified by ascii and index.

Return Value

Type: System.String
The Unicode equivalent of the IDNA substring specified by the ascii, index, and count parameters.


ascii is null.


index or count is less than zero.


index is greater than the length of ascii.


index is greater than the length of ascii minus count.


ascii is invalid based on the AllowUnassigned and UseStd3AsciiRules properties, and the IDNA standard.

For more information about domain names, labels, and label separators, see the remarks for the IdnMapping.GetAscii(String, Int32, Int32) method.

The following code example uses the GetAscii(String, Int32, Int32) method to convert a domain name to a domain name that complies with the IDNA standard. The GetUnicode(String, Int32, Int32) method then converts the standardized domain name back into the original domain name, except that the original label separators are replaced with the standard label separator.

// This example demonstrates the GetAscii and GetUnicode methods. 
// For sake of illustration, this example uses the most complex 
// form of those methods, not the most convenient. 

using System;
using System.Globalization;

class Sample 
    public static void Main() 
   Define a domain name consisting of the labels: GREEK SMALL LETTER 
   THETA (U+03B8); FULLWIDTH FULL STOP (U+FF0E); and "com".
    string name = "\u03C0\u3002\u03B8\uFF0Ecom";
    string international;
    string nonInternational;

    string msg1 = "the original non-internationalized \ndomain name:";
    string msg2 = "Allow unassigned characters?:     {0}";
    string msg3 = "Use non-internationalized rules?: {0}";
    string msg4 = "Convert the non-internationalized domain name to international format...";
    string msg5 = "Display the encoded domain name:\n\"{0}\"";
    string msg6 = "the encoded domain name:";
    string msg7 = "Convert the internationalized domain name to non-international format...";
    string msg8 = "the reconstituted non-internationalized \ndomain name:";
    string msg9 = "Visually compare the code points of the reconstituted string to the " +
                  "original.\n" +
                  "Note that the reconstituted string contains standard label " +
                  "separators (U+002e).";
// ----------------------------------------------------------------------------
    CodePoints(name, msg1);
// ----------------------------------------------------------------------------

    IdnMapping idn = new IdnMapping();

    Console.WriteLine(msg2, idn.AllowUnassigned);
    Console.WriteLine(msg3, idn.UseStd3AsciiRules);
// ----------------------------------------------------------------------------
    international = idn.GetAscii(name, 0, name.Length);
    Console.WriteLine(msg5, international);
    CodePoints(international, msg6);
// ----------------------------------------------------------------------------
    nonInternational = idn.GetUnicode(international, 0, international.Length);
    CodePoints(nonInternational, msg8);
// ---------------------------------------------------------------------------- 
    static void CodePoints(string value, string title)
    Console.WriteLine("Display the Unicode code points of {0}", title);
    foreach (char c in value) 
        Console.Write("{0:x4} ", Convert.ToInt32(c));
This code example produces the following results:

Display the Unicode code points of the original non-internationalized
domain name:
03c0 3002 03b8 ff0e 0063 006f 006d

Allow unassigned characters?:     False
Use non-internationalized rules?: False

Convert the non-internationalized domain name to international format...
Display the encoded domain name:

Display the Unicode code points of the encoded domain name:
0078 006e 002d 002d 0031 0078 0061 002e 0078 006e 002d 002d 0074 0078 0061 002e 0063 006f

Convert the internationalized domain name to non-international format...
Display the Unicode code points of the reconstituted non-internationalized
domain name:
03c0 002e 03b8 002e 0063 006f 006d

Visually compare the code points of the reconstituted string to the original.
Note that the reconstituted string contains standard label separators (U+002e).


Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0