TextElementEnumerator Class

TextElementEnumerator Class

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Enumerates the text elements of a string.


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

public class TextElementEnumerator : IEnumerator

The TextElementEnumerator type exposes the following members.

Public propertyCurrentGets the current text element in the string.
Public propertyElementIndexGets the index of the text element that the enumerator is currently positioned over.

Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetTextElementGets the current text element in the string.
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodMoveNextAdvances the enumerator to the next text element of the string.
Public methodResetSets the enumerator to its initial position, which is before the first text element in the string.
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)

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.

Text element enumerators are intended to be used only to read data in the string. Enumerators cannot be used to modify the underlying string.

The enumerator does not have exclusive access to the string.

When an enumerator is created, it takes a snapshot of the current state of the string. If changes are made to the string, such as adding, modifying, or deleting text elements, the snapshot gets out of sync and the enumerator throws an InvalidOperationException. Two enumerators created from the same string at the same time can have different snapshots of 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. Whenever 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 a 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 shows the values returned by TextElementEnumerator.

using System;
using System.Globalization;

public class Example

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)

      // Creates and initializes a String containing the following:
      //   - a surrogate pair (high surrogate U+D800 and low surrogate U+DC00)
      //   - a combining character sequence (the Latin small letter "a" followed by the combining grave accent)
      //   - a base character (the ligature "")
      String myString = "\uD800\uDC00\u0061\u0300\u00C6";

      // Creates and initializes a TextElementEnumerator for myString.
      TextElementEnumerator myTEE = StringInfo.GetTextElementEnumerator(myString);

      // Displays the values returned by ElementIndex, Current and GetTextElement.
      // Current and GetTextElement return a string containing the entire text element. 
      outputBlock.Text += "Index\tCurrent\tGetTextElement" + "\n";
      while (myTEE.MoveNext())
         outputBlock.Text += String.Format("[{0}]:\t{1}\t{2}", myTEE.ElementIndex, myTEE.Current, myTEE.GetTextElement()) + "\n";



This code produces the following output.  The question marks take the place of high and low surrogates.

Index   Current GetTextElement
[0]:    ??      ??
[2]:    a`      a`
[4]:    Æ       Æ


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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