TextFragment Class

TextFragment Class


Contains text and speech attribute information for consumption by a speech synthsizer engine.

Namespace:   System.Speech.Synthesis.TtsEngine
Assembly:  System.Speech (in System.Speech.dll)


Public Class TextFragment


Constructs a new instance of TextFragment.


Gets or sets speech attribute information for a TextFragment.


Gets or sets the length of the speech text in the fragment.


Gets or sets the starting location of the text in the fragment.


Sets or gets the speech text of the fragment.


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)


Serves as the default hash function. (Inherited from Object.)


Gets the Type of the current instance.(Inherited from Object.)


Creates a shallow copy of the current Object.(Inherited from Object.)


Returns a string that represents the current object.(Inherited from Object.)

The Speech platform infrastructure unpacks the XML based structure of the SSML input and constructs TextFragment objects.

Speech content is available through the TextLength, TextOffset, and TextToSpeak properties of a TextFragment instance.

Speech attribute information, such as emphasis, pitch, and rate, are obtained from the FragmentState object returned by the TextFragmentState property.

The example below is part of a custom speech synthesis implementation inheriting from TtsEngineSsml, and using the use of TextFragment, SpeechEventInfo, FragmentState, and T:System.Speech.Synthesis.TtsEngine.TtsEventID.

The implementation of M:System.Speech.Synthesis.TtsEngine.TtsEngineSsml.Speak

  1. Receives an array of TextFragment instances and creates a new array of TextFragment instances to be passed to the Speak method on an underlying synthesis engine.

    Particular care is used to respect the TextOffset, TextLength on the original TextFragment when creating the TextToSpeak on the new TextFragment instances.

  2. If the TtsEngineAction enumeration value by found from the Action property on the FragmentState returned by the State property of each TextFragment instance is Speak, the implementation

    • Translates Americanism to Britishisms in the text to be spoken.

    • If the EventInterest property on the ITtsEngineSite interfaces provided to the implementation support the WordBoundary event type, a SpeechEventInfo instance is used to create an event to drive a synthesizer progress meter is created.

  3. A speech rendering engine is then called with the modified TextFragment array.

private const int WordBoundaryFlag = 1 << (int)TtsEventId.WordBoundary;
private readonly char[] spaces = new char[] { ' ', '\t', '\r', '\n' };
internal struct UsVsUk
  internal string UK;
  internal string US;

override public void Speak (TextFragment [] frags, IntPtr wfx, ITtsEngineSite site)
  TextFragment [] newFrags=new TextFragment[frags.Length];

  for (int i=0;i<frags.Length;i++){
    newFrags[i].TextToSpeak = frags[i].TextToSpeak.Substring(frags[i].TextOffset,
    newFrags[i].TextLength = newFrags[i].TextToSpeak.Length;
    newFrags[i].TextOffset = 0;
    if (newFrags[i].State.Action == TtsEngineAction.Speak) {
      //Us to UK conversion
      foreach (UsVsUk term in TransList) {
      newFrags[i].TextToSpeak.Replace(term.US, term.UK);
      //Generate progress meter events if supported
      if ((site.EventInterest & WordBoundaryFlag) != 0) {
      string[] subs = newFrags[i].TextToSpeak.Split(spaces);

      foreach (string s in subs) {
        int offset = newFrags[i].TextOffset;
        SpeechEventInfo spEvent = new SpeechEventInfo((Int16)TtsEventId.WordBoundary, 
                 s.Length, new IntPtr(offset));
        offset += s.Length;
        if (s.Trim().Length > 0) {
          SpeechEventInfo[] events = new SpeechEventInfo[1];
          events[0] = spEvent;
          site.AddEvents(events, 1);

  _baseSynthesize.Speak(newFrags, wfx, site);


.NET Framework
Available since 3.0

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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