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StringInfo.ParseCombiningCharacters Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Returns the index of each base character, high surrogate, or control character within the specified string.

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

Syntax

'Declaration
Public Shared Function ParseCombiningCharacters ( _
    str As String _
) As Integer()

public static int[] ParseCombiningCharacters(
    string str
)

Parameters

Return Value

Type: array<System.Int32[]
An array of integers that contains the zero-based index of each base character, high surrogate, or control character within the specified string.

Exceptions

Exception Condition
ArgumentNullException

str is nulla null reference (Nothing in Visual Basic).

Remarks

The Unicode Standard defines a surrogate pair as a coded character representation for a single abstract character that consists of a sequence of two code units, where the first unit of the pair is a high surrogate and the second is a low surrogate. A high surrogate is a Unicode code point in the range U+D800 through U+DBFF and a low surrogate is a Unicode code point in the range U+DC00 through U+DFFF.

A control character is a character for which the Unicode value is U+007F or in the range U+0000 through U+001F or U+0080 through U+009F.

The .NET Framework defines a text element as a unit of text that is displayed as a single character, that is, a grapheme. A text element can be a base character, a surrogate pair, or a combining character sequence. The Unicode Standard defines a combining character sequence as a combination of a base character and one or more combining characters. A surrogate pair can represent a base character or a combining character. For more information on surrogate pairs and combining character sequences, see The Unicode Standard at http://www.unicode.org..

If a combining character sequence is invalid, every combining character in that sequence is also returned.

Each index in the resulting array is the beginning of a text element, that is, the index of the base character or the high surrogate.

The length of each element is easily computed as the difference between successive indexes. The length of the array will always be less than or equal to the length of the string. For example, given the string "\u4f00\u302a\ud800\udc00\u4f01", this method would return the indexes 0, 2, and 4.

Examples

The following code example demonstrates calling the ParseCombiningCharacters method. This code example is part of a larger example provided for the StringInfo class.

Imports System.Globalization
Imports System.Text

Module Example
   Public Sub Demo(outputBlock As System.Windows.Controls.TextBlock)
      ' The string below contains combining characters.
      Dim chars() As Char = {"a"c, ChrW(&h0304), ChrW(&h0308), "b"c, "c"c, ChrW(&h0327)}
      Dim s As New String(chars)

      ' Show each 'character' in the string.
      EnumTextElements(outputBlock, s)

      ' Show the index in the string where each 'character' starts.
      EnumTextElementIndexes(outputBlock, s)
   End Sub

   ' Show how to enumerate each real character (honoring surrogates) in a string.
   Private Sub EnumTextElements(outputBlock As System.Windows.Controls.TextBlock, s As String)
      ' This StringBuilder holds the output results.
      Dim sb As New StringBuilder()

      ' Use the enumerator returned from GetTextElementEnumerator 
      ' method to examine each real character.
      Dim charEnum As TextElementEnumerator = StringInfo.GetTextElementEnumerator(s)
      Do While charEnum.MoveNext()
         sb.AppendFormat("Character at index {0} is '{1}'{2}", _
                         charEnum.ElementIndex, charEnum.GetTextElement(), vbCrLf)
      Loop

      ' Show the results.
      outputBlock.Text &= "Result of GetTextElementEnumerator:" & vbCrLf
      outputBlock.Text &= sb.ToString() & vbCrLf
   End Sub

   ' Show how to discover the index of each real character (honoring surrogates) in a string.
   Private Sub EnumTextElementIndexes(outputBlock As System.Windows.Controls.TextBlock, s As String)
      ' This StringBuilder holds the output results.
      Dim sb As New StringBuilder()

      ' Use the ParseCombiningCharacters method to 
      ' get the index of each real character in the string.
      Dim textElemIndex() As Integer = StringInfo.ParseCombiningCharacters(s)

      ' Iterate through each real character showing the character and the index where it was found.
      For i As Integer = 0 To textElemIndex.Length - 1
         sb.AppendFormat("Character {0} starts at index {1}{2}", _
                         i, textElemIndex(i), vbCrLf)
      Next

      ' Show the results.
      outputBlock.Text &= "Result of ParseCombiningCharacters:" & vbCrLf
      outputBlock.Text &= sb.ToString() & vbCrLf
   End Sub
End Module
' This code produces the following output.
'
' Result of GetTextElementEnumerator:
' Character at index 0 is 'a-"'
' Character at index 3 is 'b'
' Character at index 4 is 'c,'
' 
' Result of ParseCombiningCharacters:
' Character 0 starts at index 0
' Character 1 starts at index 3
' Character 2 starts at index 4

using System;
using System.Text;
using System.Globalization;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // The string below contains combining characters.
      String s = "a\u0304\u0308bc\u0327";

      // Show each 'character' in the string.
      EnumTextElements(outputBlock, s);

      // Show the index in the string where each 'character' starts.
      EnumTextElementIndexes(outputBlock, s);
   }

   // Show how to enumerate each real character (honoring surrogates) in a string.
   static void EnumTextElements(System.Windows.Controls.TextBlock outputBlock, String s)
   {
      // This StringBuilder holds the output results.
      StringBuilder sb = new StringBuilder();

      // Use the enumerator returned from GetTextElementEnumerator 
      // method to examine each real character.
      TextElementEnumerator charEnum = StringInfo.GetTextElementEnumerator(s);
      while (charEnum.MoveNext())
      {
         sb.AppendFormat(
           "Character at index {0} is '{1}'\n",
           charEnum.ElementIndex, charEnum.GetTextElement());
      }

      // Show the results.
      outputBlock.Text += "Result of GetTextElementEnumerator:" + "\n";
      outputBlock.Text += sb + "\n";
   }

   // Show how to discover the index of each real character (honoring surrogates) in a string.
   static void EnumTextElementIndexes(System.Windows.Controls.TextBlock outputBlock, String s)
   {
      // This StringBuilder holds the output results.
      StringBuilder sb = new StringBuilder();

      // Use the ParseCombiningCharacters method to 
      // get the index of each real character in the string.
      Int32[] textElemIndex = StringInfo.ParseCombiningCharacters(s);

      // Iterate through each real character showing the character and the index where it was found.
      for (Int32 i = 0; i < textElemIndex.Length; i++)
      {
         sb.AppendFormat(
            "Character {0} starts at index {1}\n", i, textElemIndex[i]);
      }

      // Show the results.
      outputBlock.Text += "Result of ParseCombiningCharacters:" + "\n";
      outputBlock.Text += sb + "\n";
   }
}

// This code produces the following output.
//
// Result of GetTextElementEnumerator:
// Character at index 0 is 'a-"'
// Character at index 3 is 'b'
// Character at index 4 is 'c,'
// 
// Result of ParseCombiningCharacters:
// Character 0 starts at index 0
// Character 1 starts at index 3
// Character 2 starts at index 4

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

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