Normalization
Some Unicode characters have multiple equivalent binary representations consisting of sets of combining and/or composite Unicode characters. Multiple representations for a single character complicate searching, sorting, matching, and other operations.
The Unicode Standard defines a process called normalization that returns one binary representation for any of the equivalent binary representations of a character. Normalization can use several algorithms, called normalization forms, that obey different rules. The .NET Framework currently supports Unicode normalization forms C, D, KC, and KD.
Note
Two strings normalized to the same normalization form can be compared using an ordinal comparison, that is, a character-by-character binary comparison.
For more information about the normalization forms supported by the .NET Framework, see NormalizationForm. For more information about normalization, character decompositions, and equivalence, see Unicode Standard Annex #15, "Unicode Normalization Forms," at the Unicode home page.
Normalizing a String
The application should use the String.Normalize method of a String object to return a new string that is normalized by default to normalization form C. Alternatively, the application can use the String.Normalize method of a String object, specifying a NormalizationForm value, to return a new string that is normalized specifically to normalization form C, D, KC, or KD.
Testing to Determine if a String is Normalized
Your application can use the String.IsNormalized method of a String object to determine if the string value of the object is normalized to normalization form C. As an alternative, the application can use the String.IsNormalized method of a String object, specifying a particular NormalizationForm value, to determine if the string value of the object is normalized specifically to normalization form C, D, KC, or KD.
Example
The following code example demonstrates the IsNormalized and Normalize methods. The code example tests to determine if an original string is in any of the four normalization forms, creates a version of the original string in each of the normalization forms, tests to determine if each normalized string is in the intended normalization form, then displays the hexadecimal code point of each character in each normalized string.
' This example demonstrates the String.Normalize method
' and the String.IsNormalized method
Imports System
Imports System.Text
Imports Microsoft.VisualBasic
Class Sample
Public Shared Sub Main()
' Character c; combining characters acute and cedilla; character 3/4
Dim s1 = New [String](New Char() {ChrW(&H0063), ChrW(&H0301), ChrW(&H0327), ChrW(&H00BE)})
Dim s2 As String = Nothing
Dim divider = New [String]("-"c, 80)
divider = [String].Concat(Environment.NewLine, divider, Environment.NewLine)
Try
Show("s1", s1)
Console.WriteLine()
Console.WriteLine("U+0063 = LATIN SMALL LETTER C")
Console.WriteLine("U+0301 = COMBINING ACUTE ACCENT")
Console.WriteLine("U+0327 = COMBINING CEDILLA")
Console.WriteLine("U+00BE = VULGAR FRACTION THREE QUARTERS")
Console.WriteLine(divider)
Console.WriteLine("A1) Is s1 normalized to the default form (Form C)?: {0}", s1.IsNormalized())
Console.WriteLine("A2) Is s1 normalized to Form C?: {0}", s1.IsNormalized(NormalizationForm.FormC))
Console.WriteLine("A3) Is s1 normalized to Form D?: {0}", s1.IsNormalized(NormalizationForm.FormD))
Console.WriteLine("A4) Is s1 normalized to Form KC?: {0}", s1.IsNormalized(NormalizationForm.FormKC))
Console.WriteLine("A5) Is s1 normalized to Form KD?: {0}", s1.IsNormalized(NormalizationForm.FormKD))
Console.WriteLine(divider)
Console.WriteLine("Set string s2 to each normalized form of string s1.")
Console.WriteLine()
Console.WriteLine("U+1E09 = LATIN SMALL LETTER C WITH CEDILLA AND ACUTE")
Console.WriteLine("U+0033 = DIGIT THREE")
Console.WriteLine("U+2044 = FRACTION SLASH")
Console.WriteLine("U+0034 = DIGIT FOUR")
Console.WriteLine(divider)
s2 = s1.Normalize()
Console.Write("B1) Is s2 normalized to the default form (Form C)?: ")
Console.WriteLine(s2.IsNormalized())
Show("s2", s2)
Console.WriteLine()
s2 = s1.Normalize(NormalizationForm.FormC)
Console.Write("B2) Is s2 normalized to Form C?: ")
Console.WriteLine(s2.IsNormalized(NormalizationForm.FormC))
Show("s2", s2)
Console.WriteLine()
s2 = s1.Normalize(NormalizationForm.FormD)
Console.Write("B3) Is s2 normalized to Form D?: ")
Console.WriteLine(s2.IsNormalized(NormalizationForm.FormD))
Show("s2", s2)
Console.WriteLine()
s2 = s1.Normalize(NormalizationForm.FormKC)
Console.Write("B4) Is s2 normalized to Form KC?: ")
Console.WriteLine(s2.IsNormalized(NormalizationForm.FormKC))
Show("s2", s2)
Console.WriteLine()
s2 = s1.Normalize(NormalizationForm.FormKD)
Console.Write("B5) Is s2 normalized to Form KD?: ")
Console.WriteLine(s2.IsNormalized(NormalizationForm.FormKD))
Show("s2", s2)
Console.WriteLine()
Catch e As Exception
Console.WriteLine(e.Message)
End Try
End Sub 'Main
Private Shared Sub Show(title As String, s As String)
Console.Write("Characters in string {0} = ", title)
Dim x As Char
For Each x In s.ToCharArray()
Console.Write("{0:X4} ", AscW(x))
Next x
Console.WriteLine()
End Sub 'Show
End Class 'Sample
'
'This example produces the following results:
'
'Characters in string s1 = 0063 0301 0327 00BE
'
'U+0063 = LATIN SMALL LETTER C
'U+0301 = COMBINING ACUTE ACCENT
'U+0327 = COMBINING CEDILLA
'U+00BE = VULGAR FRACTION THREE QUARTERS
'
'--------------------------------------------------------------------------------
'
'A1) Is s1 normalized to the default form (Form C)?: False
'A2) Is s1 normalized to Form C?: False
'A3) Is s1 normalized to Form D?: False
'A4) Is s1 normalized to Form KC?: False
'A5) Is s1 normalized to Form KD?: False
'
'--------------------------------------------------------------------------------
'
'Set string s2 to each normalized form of string s1.
'
'U+1E09 = LATIN SMALL LETTER C WITH CEDILLA AND ACUTE
'U+0033 = DIGIT THREE
'U+2044 = FRACTION SLASH
'U+0034 = DIGIT FOUR
'
'--------------------------------------------------------------------------------
'
'B1) Is s2 normalized to the default form (Form C)?: True
'Characters in string s2 = 1E09 00BE
'
'B2) Is s2 normalized to Form C?: True
'Characters in string s2 = 1E09 00BE
'
'B3) Is s2 normalized to Form D?: True
'Characters in string s2 = 0063 0327 0301 00BE
'
'B4) Is s2 normalized to Form KC?: True
'Characters in string s2 = 1E09 0033 2044 0034
'
'B5) Is s2 normalized to Form KD?: True
'Characters in string s2 = 0063 0327 0301 0033 2044 0034
'
// This example demonstrates the String.Normalize method
// and the String.IsNormalized method
using System;
using System.Text;
class Sample
{
public static void Main()
{
// Character c; combining characters acute and cedilla; character 3/4
string s1 = new String( new char[] {'\u0063', '\u0301', '\u0327', '\u00BE'});
string s2 = null;
string divider = new String('-', 80);
divider = String.Concat(Environment.NewLine, divider, Environment.NewLine);
try
{
Show("s1", s1);
Console.WriteLine();
Console.WriteLine("U+0063 = LATIN SMALL LETTER C");
Console.WriteLine("U+0301 = COMBINING ACUTE ACCENT");
Console.WriteLine("U+0327 = COMBINING CEDILLA");
Console.WriteLine("U+00BE = VULGAR FRACTION THREE QUARTERS");
Console.WriteLine(divider);
Console.WriteLine("A1) Is s1 normalized to the default form (Form C)?: {0}",
s1.IsNormalized());
Console.WriteLine("A2) Is s1 normalized to Form C?: {0}",
s1.IsNormalized(NormalizationForm.FormC));
Console.WriteLine("A3) Is s1 normalized to Form D?: {0}",
s1.IsNormalized(NormalizationForm.FormD));
Console.WriteLine("A4) Is s1 normalized to Form KC?: {0}",
s1.IsNormalized(NormalizationForm.FormKC));
Console.WriteLine("A5) Is s1 normalized to Form KD?: {0}",
s1.IsNormalized(NormalizationForm.FormKD));
Console.WriteLine(divider);
Console.WriteLine("Set string s2 to each normalized form of string s1.");
Console.WriteLine();
Console.WriteLine("U+1E09 = LATIN SMALL LETTER C WITH CEDILLA AND ACUTE");
Console.WriteLine("U+0033 = DIGIT THREE");
Console.WriteLine("U+2044 = FRACTION SLASH");
Console.WriteLine("U+0034 = DIGIT FOUR");
Console.WriteLine(divider);
s2 = s1.Normalize();
Console.Write("B1) Is s2 normalized to the default form (Form C)?: ");
Console.WriteLine(s2.IsNormalized());
Show("s2", s2);
Console.WriteLine();
s2 = s1.Normalize(NormalizationForm.FormC);
Console.Write("B2) Is s2 normalized to Form C?: ");
Console.WriteLine(s2.IsNormalized(NormalizationForm.FormC));
Show("s2", s2);
Console.WriteLine();
s2 = s1.Normalize(NormalizationForm.FormD);
Console.Write("B3) Is s2 normalized to Form D?: ");
Console.WriteLine(s2.IsNormalized(NormalizationForm.FormD));
Show("s2", s2);
Console.WriteLine();
s2 = s1.Normalize(NormalizationForm.FormKC);
Console.Write("B4) Is s2 normalized to Form KC?: ");
Console.WriteLine(s2.IsNormalized(NormalizationForm.FormKC));
Show("s2", s2);
Console.WriteLine();
s2 = s1.Normalize(NormalizationForm.FormKD);
Console.Write("B5) Is s2 normalized to Form KD?: ");
Console.WriteLine(s2.IsNormalized(NormalizationForm.FormKD));
Show("s2", s2);
Console.WriteLine();
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
}
private static void Show(string title, string s)
{
Console.Write("Characters in string {0} = ", title);
foreach(short x in s.ToCharArray())
{
Console.Write("{0:X4} ", x);
}
Console.WriteLine();
}
}
/*
This example produces the following results:
Characters in string s1 = 0063 0301 0327 00BE
U+0063 = LATIN SMALL LETTER C
U+0301 = COMBINING ACUTE ACCENT
U+0327 = COMBINING CEDILLA
U+00BE = VULGAR FRACTION THREE QUARTERS
--------------------------------------------------------------------------------
A1) Is s1 normalized to the default form (Form C)?: False
A2) Is s1 normalized to Form C?: False
A3) Is s1 normalized to Form D?: False
A4) Is s1 normalized to Form KC?: False
A5) Is s1 normalized to Form KD?: False
--------------------------------------------------------------------------------
Set string s2 to each normalized form of string s1.
U+1E09 = LATIN SMALL LETTER C WITH CEDILLA AND ACUTE
U+0033 = DIGIT THREE
U+2044 = FRACTION SLASH
U+0034 = DIGIT FOUR
--------------------------------------------------------------------------------
B1) Is s2 normalized to the default form (Form C)?: True
Characters in string s2 = 1E09 00BE
B2) Is s2 normalized to Form C?: True
Characters in string s2 = 1E09 00BE
B3) Is s2 normalized to Form D?: True
Characters in string s2 = 0063 0327 0301 00BE
B4) Is s2 normalized to Form KC?: True
Characters in string s2 = 1E09 0033 2044 0034
B5) Is s2 normalized to Form KD?: True
Characters in string s2 = 0063 0327 0301 0033 2044 0034
*/
// This example demonstrates the String.Normalize method
// and the String.IsNormalized method
using namespace System;
using namespace System::Text;
void Show( String^ title, String^ s )
{
Console::Write( "Characters in string {0} = ", title );
System::Collections::IEnumerator^ myEnum = s->ToCharArray()->GetEnumerator();
while ( myEnum->MoveNext() )
{
/*) * __try_cast < Char * > ( myEnum -> Current );*/
int x;
Console::Write( "{0:X4} ", x );
}
Console::WriteLine();
}
int main()
{
// Character c; combining characters acute and cedilla; character 3/4
array<Char>^temp0 = {L'c',L'\u0301',L'\u0327',L'\u00BE'};
String^ s1 = gcnew String( temp0 );
String^ s2 = nullptr;
String^ divider = gcnew String( '-',80 );
divider = String::Concat( Environment::NewLine, divider, Environment::NewLine );
try
{
Show( "s1", s1 );
Console::WriteLine();
Console::WriteLine( "U+0063 = LATIN SMALL LETTER C" );
Console::WriteLine( "U+0301 = COMBINING ACUTE ACCENT" );
Console::WriteLine( "U+0327 = COMBINING CEDILLA" );
Console::WriteLine( "U+00BE = VULGAR FRACTION THREE QUARTERS" );
Console::WriteLine( divider );
Console::WriteLine( "A1) Is s1 normalized to the default form (Form C)?: {0}", s1->IsNormalized() );
Console::WriteLine( "A2) Is s1 normalized to Form C?: {0}", s1->IsNormalized( NormalizationForm::FormC ) );
Console::WriteLine( "A3) Is s1 normalized to Form D?: {0}", s1->IsNormalized( NormalizationForm::FormD ) );
Console::WriteLine( "A4) Is s1 normalized to Form KC?: {0}", s1->IsNormalized( NormalizationForm::FormKC ) );
Console::WriteLine( "A5) Is s1 normalized to Form KD?: {0}", s1->IsNormalized( NormalizationForm::FormKD ) );
Console::WriteLine( divider );
Console::WriteLine( "Set string s2 to each normalized form of string s1." );
Console::WriteLine();
Console::WriteLine( "U+1E09 = LATIN SMALL LETTER C WITH CEDILLA AND ACUTE" );
Console::WriteLine( "U+0033 = DIGIT THREE" );
Console::WriteLine( "U+2044 = FRACTION SLASH" );
Console::WriteLine( "U+0034 = DIGIT FOUR" );
Console::WriteLine( divider );
s2 = s1->Normalize();
Console::Write( "B1) Is s2 normalized to the default form (Form C)?: " );
Console::WriteLine( s2->IsNormalized() );
Show( "s2", s2 );
Console::WriteLine();
s2 = s1->Normalize( NormalizationForm::FormC );
Console::Write( "B2) Is s2 normalized to Form C?: " );
Console::WriteLine( s2->IsNormalized( NormalizationForm::FormC ) );
Show( "s2", s2 );
Console::WriteLine();
s2 = s1->Normalize( NormalizationForm::FormD );
Console::Write( "B3) Is s2 normalized to Form D?: " );
Console::WriteLine( s2->IsNormalized( NormalizationForm::FormD ) );
Show( "s2", s2 );
Console::WriteLine();
s2 = s1->Normalize( NormalizationForm::FormKC );
Console::Write( "B4) Is s2 normalized to Form KC?: " );
Console::WriteLine( s2->IsNormalized( NormalizationForm::FormKC ) );
Show( "s2", s2 );
Console::WriteLine();
s2 = s1->Normalize( NormalizationForm::FormKD );
Console::Write( "B5) Is s2 normalized to Form KD?: " );
Console::WriteLine( s2->IsNormalized( NormalizationForm::FormKD ) );
Show( "s2", s2 );
Console::WriteLine();
}
catch ( Exception^ e )
{
Console::WriteLine( e->Message );
}
}
/*
This example produces the following results:
Characters in string s1 = 0063 0301 0327 00BE
U+0063 = LATIN SMALL LETTER C
U+0301 = COMBINING ACUTE ACCENT
U+0327 = COMBINING CEDILLA
U+00BE = VULGAR FRACTION THREE QUARTERS
--------------------------------------------------------------------------------
A1) Is s1 normalized to the default form (Form C)?: False
A2) Is s1 normalized to Form C?: False
A3) Is s1 normalized to Form D?: False
A4) Is s1 normalized to Form KC?: False
A5) Is s1 normalized to Form KD?: False
--------------------------------------------------------------------------------
Set string s2 to each normalized form of string s1.
U+1E09 = LATIN SMALL LETTER C WITH CEDILLA AND ACUTE
U+0033 = DIGIT THREE
U+2044 = FRACTION SLASH
U+0034 = DIGIT FOUR
--------------------------------------------------------------------------------
B1) Is s2 normalized to the default form (Form C)?: True
Characters in string s2 = 1E09 00BE
B2) Is s2 normalized to Form C?: True
Characters in string s2 = 1E09 00BE
B3) Is s2 normalized to Form D?: True
Characters in string s2 = 0063 0327 0301 00BE
B4) Is s2 normalized to Form KC?: True
Characters in string s2 = 1E09 0033 2044 0034
B5) Is s2 normalized to Form KD?: True
Characters in string s2 = 0063 0327 0301 0033 2044 0034
*/