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SpeechRecognizer.StateChanged Event


Occurs when the running state of the Windows Desktop Speech Technology recognition engine changes.

 event EventHandler<System::Speech::Recognition::StateChangedEventArgs ^> ^ StateChanged;
public event EventHandler<System.Speech.Recognition.StateChangedEventArgs> StateChanged;
member this.StateChanged : EventHandler<System.Speech.Recognition.StateChangedEventArgs> 
Public Event StateChanged As EventHandler(Of StateChangedEventArgs) 
Public Custom Event StateChanged As EventHandler(Of StateChangedEventArgs) 

Event Type


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 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");  


The shared recognizer raises this event when the state of Windows Speech Recognition changes to the Listening or Stopped state.

To get the state of the shared recognizer at the time of the event, use the RecognizerState property of the associated StateChangedEventArgs. To get the current state of the shared recognizer, use the recognizer's State property.

When you create a delegate for a StateChanged event, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event-handler delegates, see Events and Delegates.

Applies to

See also