StringInfo.GetTextElementEnumerator Method (String)

Updated: December 2010

Returns an enumerator that iterates through the text elements of the entire string.

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

public static TextElementEnumerator GetTextElementEnumerator(
	string str
)

Parameters

str
Type: System.String

The string to iterate through.

Return Value

Type: System.Globalization.TextElementEnumerator
A TextElementEnumerator for the entire string.

ExceptionCondition
ArgumentNullException

str is null.

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 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. 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..

The text element enumerator is used only to read data in the string; it cannot modify the underlying string. The enumerator does not have exclusive access to the string.

The enumerator is in an invalid state if it is positioned before the first text element in the string or after the last text element in the string. When the enumerator is in an invalid state, calling Current throws an exception.

Initially, the enumerator is positioned before the first text element in the string. Reset also brings the enumerator back to this position. Therefore, after an enumerator is created or after Reset is called, MoveNext must be called to advance the enumerator to the first text element of the string before reading the value of Current.

Current returns the same object until either MoveNext or Reset is called.

After the end of the string is passed, the enumerator is again in an invalid state and calling MoveNext returns false. Calling Current throws an exception if the last call to MoveNext returned false.

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

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

public sealed class App {
   static void Main() {
      // The string below contains combining characters.
      String s = "a\u0304\u0308bc\u0327";

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

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

   // Show how to enumerate each real character (honoring surrogates) in a string. 
   static void EnumTextElements(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}'{2}",
           charEnum.ElementIndex, charEnum.GetTextElement(),
           Environment.NewLine);
      }

      // Show the results.
      Console.WriteLine("Result of GetTextElementEnumerator:");
      Console.WriteLine(sb);
   }

   // Show how to discover the index of each real character (honoring surrogates) in a string. 
   static void EnumTextElementIndexes(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}{2}",
            i, textElemIndex[i], Environment.NewLine);
      }

      // Show the results.
      Console.WriteLine("Result of ParseCombiningCharacters:");
      Console.WriteLine(sb);
   }
}

// 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

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, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

December 2010

Removed information about operations that cause the enumerator to throw an InvalidOperationException.

Customer feedback.

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