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StateChangedEventArgs Class


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Returns data from the StateChanged event.

Namespace:   System.Speech.Recognition
Assembly:  System.Speech (in System.Speech.dll)


public class StateChangedEventArgs : EventArgs


Gets the current state of the shared speech recognition engine in Windows.


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 StateChanged event is raised by the SpeechRecognizer class. StateChangedEventArgs derives from EventArgs and is passed to handlers for StateChanged events.

State is a read-only property. A shared speech recognizer's state cannot be changed programmatically. Users can change a shared speech recognizer's state using the Speech Recognition user interface (UI) or through the Speech Recognition member of the Windows Control Panel.

Both the On and Sleep settings in the Speech Recognition UI correspond to the Listening state. The Off setting in the Speech Recognition UI corresponds to Stopped.

The following example creates a shared speech recognizer, and then creates two types of grammars for recognizing specific words and for accepting free dictation. The example asynchronously loads all the created grammars to the recognizer. A handler for the StateChanged event uses the EmulateRecognizeAsync method to put Windows Recognition in "listening" mode.

using System;
using System.Speech.Recognition;

namespace SampleRecognition
  class Program
    private static SpeechRecognizer recognizer;
    public static void Main(string[] args)

      // Initialize a shared speech recognition engine.
      recognizer = new SpeechRecognizer();

      // Add a handler for the LoadGrammarCompleted event.
      recognizer.LoadGrammarCompleted += new EventHandler<LoadGrammarCompletedEventArgs>(recognizer_LoadGrammarCompleted);

      // Add a handler for the SpeechRecognized event.
      recognizer.SpeechRecognized += new EventHandler<SpeechRecognizedEventArgs>(recognizer_SpeechRecognized);

      // Add a handler for the StateChanged event.
      recognizer.StateChanged += new EventHandler<StateChangedEventArgs>(recognizer_StateChanged);

      // Create "yesno" grammar.
      Choices yesChoices = new Choices(new string[] { "yes", "yup", "yah}" });
      SemanticResultValue yesValue =
          new SemanticResultValue(yesChoices, (bool)true);
      Choices noChoices = new Choices(new string[] { "no", "nope", "nah" });
      SemanticResultValue noValue = new SemanticResultValue(noChoices, (bool)false);
      SemanticResultKey yesNoKey =
          new SemanticResultKey("yesno", new Choices(new GrammarBuilder[] { yesValue, noValue }));
      Grammar yesnoGrammar = new Grammar(yesNoKey);
      yesnoGrammar.Name = "yesNo";

      // Create "done" grammar.
      Grammar doneGrammar =
        new Grammar(new Choices(new string[] { "done", "exit", "quit", "stop" }));
      doneGrammar.Name = "Done";

      // Create dictation grammar.
      Grammar dictation = new DictationGrammar();
      dictation.Name = "Dictation";

      // Load grammars to the recognizer.

      // Keep the console window open.

    // Put the shared speech recognizer into "listening" mode.
    static void  recognizer_StateChanged(object sender, StateChangedEventArgs e)
     if (e.RecognizerState != RecognizerState.Stopped)
        recognizer.EmulateRecognizeAsync("Start listening");

    // Write the grammar name and the text of the recognized phrase to the console.
    static void  recognizer_SpeechRecognized(object sender, SpeechRecognizedEventArgs e)
     Console.WriteLine("Grammar({0}): {1}", e.Result.Grammar.Name, e.Result.Text);

      // Add event handler code here.

    // Handle the LoadGrammarCompleted event.
    static void  recognizer_LoadGrammarCompleted(object sender, LoadGrammarCompletedEventArgs e)
     string grammarName = e.Grammar.Name;
      bool grammarLoaded = e.Grammar.Loaded;
      if (e.Error != null)
        Console.WriteLine("LoadGrammar for {0} failed with a {1}.",
        grammarName, e.Error.GetType().Name);

      // Add exception handling code here.
      Console.WriteLine("Grammar {0} {1} loaded.",
      grammarName, (grammarLoaded) ? "is" : "is not");

.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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