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SpeechRecognitionEngine.RecognizeAsyncStop Method

Stops asynchronous recognition after the current recognition operation completes.

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

public void RecognizeAsyncStop()

This method finalizes asynchronous recognition without truncating input. If the current asynchronous recognition operation is receiving input, the recognizer continues accepting input until the current recognition operation is completed. The recognizer raises the RecognizeCompleted or EmulateRecognizeCompleted event when an asynchronous operation is stopped, and sets the Cancelled property of the RecognizeCompletedEventArgs to true. This method stops asynchronous operations initiated by the RecognizeAsync and EmulateRecognizeAsync methods.

To immediately cancel asynchronous recognition with only the existing input, use the RecognizeAsyncCancel method.

The following example shows part of a console application that demonstrates the use of the RecognizeAsyncStop method. The example creates and loads a speech recognition grammar, initiates a continuing asynchronous recognition operation, and then pauses 2 seconds before it stops the operation. The recognizer receives input from the file, c:\temp\audioinput\sample.wav. Event handlers are included to demonstrate the events that the recognizer raises during the operation.

using System;
using System.Globalization;
using System.Speech.Recognition;
using System.Threading;

namespace AsynchronousRecognition
{
  class Program
  {
    // Indicate whether asynchronous recognition is complete.
    static bool completed;

    static void Main(string[] args)
    {
      // Create an in-process speech recognizer.
      using (SpeechRecognitionEngine recognizer =
        new SpeechRecognitionEngine(new CultureInfo("en-US")))
      {
        // Create and load a dictation grammar.
        Grammar dictation = new DictationGrammar();
        dictation.Name = "Dictation Grammar";

        recognizer.LoadGrammar(dictation);

        // Attach event handlers.
        recognizer.SpeechDetected +=
          new EventHandler<SpeechDetectedEventArgs>(
            SpeechDetectedHandler);
        recognizer.SpeechHypothesized +=
          new EventHandler<SpeechHypothesizedEventArgs>(
            SpeechHypothesizedHandler);
        recognizer.SpeechRecognitionRejected +=
          new EventHandler<SpeechRecognitionRejectedEventArgs>(
            SpeechRecognitionRejectedHandler);
        recognizer.SpeechRecognized +=
          new EventHandler<SpeechRecognizedEventArgs>(
            SpeechRecognizedHandler);
        recognizer.RecognizeCompleted +=
          new EventHandler<RecognizeCompletedEventArgs>(
            RecognizeCompletedHandler);

        // Begin asynchronous recognition from pre-recorded input.
        recognizer.SetInputToWaveFile(@"c:\temp\audioinput\sample.wav");

        completed = false;
        Console.WriteLine("Begin continuing asynchronous recognition...");
        recognizer.RecognizeAsync(RecognizeMode.Multiple);

        // Wait 2 seconds and then stop the recognition operation.
        Thread.Sleep(TimeSpan.FromSeconds(2));
        recognizer.RecognizeAsyncStop();

        // Wait for the operation to complete.
        while (!completed)
        {
          Thread.Sleep(333);
        }

        Console.WriteLine("Done.");
      }

      Console.WriteLine();
      Console.WriteLine("Press any key to exit...");
      Console.ReadKey();
    }

    // Handle the SpeechDetected event.
    static void SpeechDetectedHandler(object sender, SpeechDetectedEventArgs e)
    {
      Console.WriteLine(" In SpeechDetectedHandler:");
      Console.WriteLine(" - AudioPosition = {0}", e.AudioPosition);
    }

    // Handle the SpeechHypothesized event.
    static void SpeechHypothesizedHandler(
      object sender, SpeechHypothesizedEventArgs e)
    {
      Console.WriteLine(" In SpeechHypothesizedHandler:");
      
      string grammarName = "<not available>";
      string resultText = "<not available>";
      if (e.Result != null)
      {
        if (e.Result.Grammar != null)
        {
          grammarName = e.Result.Grammar.Name;
        }
        resultText = e.Result.Text;
      }

      Console.WriteLine(" - Grammar Name = {0}; Result Text = {1}",
        grammarName, resultText);
    }

    // Handle the SpeechRecognitionRejected event.
    static void SpeechRecognitionRejectedHandler(
      object sender, SpeechRecognitionRejectedEventArgs e)
    {
      Console.WriteLine(" In SpeechRecognitionRejectedHandler:");

      string grammarName = "<not available>";
      string resultText = "<not available>";
      if (e.Result != null)
      {
        if (e.Result.Grammar != null)
        {
          grammarName = e.Result.Grammar.Name;
        }
        resultText = e.Result.Text;
      }

      Console.WriteLine(" - Grammar Name = {0}; Result Text = {1}",
        grammarName, resultText);
    }

    // Handle the SpeechRecognized event.
    static void SpeechRecognizedHandler(
      object sender, SpeechRecognizedEventArgs e)
    {
      Console.WriteLine(" In SpeechRecognizedHandler.");

      string grammarName = "<not available>";
      string resultText = "<not available>";
      if (e.Result != null)
      {
        if (e.Result.Grammar != null)
        {
          grammarName = e.Result.Grammar.Name;
        }
        resultText = e.Result.Text;
      }

      Console.WriteLine(" - Grammar Name = {0}; Result Text = {1}",
        grammarName, resultText);
    }

    // Handle the RecognizeCompleted event.
    static void RecognizeCompletedHandler(
      object sender, RecognizeCompletedEventArgs e)
    {
      Console.WriteLine(" In RecognizeCompletedHandler.");

      if (e.Error != null)
      {
        Console.WriteLine(
          " - Error occurred during recognition: {0}", e.Error);
        return;
      }
      if (e.Cancelled)
      {
        Console.WriteLine(" - asynchronous operation canceled.");
      }
      if (e.InitialSilenceTimeout || e.BabbleTimeout)
      {
        Console.WriteLine(
          " - BabbleTimeout = {0}; InitialSilenceTimeout = {1}",
          e.BabbleTimeout, e.InitialSilenceTimeout);
        return;
      }
      if (e.InputStreamEnded)
      {
        Console.WriteLine(
          " - AudioPosition = {0}; InputStreamEnded = {1}",
          e.AudioPosition, e.InputStreamEnded);
      }
      if (e.Result != null)
      {
        Console.WriteLine(
          " - Grammar = {0}; Text = {1}; Confidence = {2}",
          e.Result.Grammar.Name, e.Result.Text, e.Result.Confidence);
      }
      else
      {
        Console.WriteLine(" - No result.");
      }

      completed = true;
    }
  }
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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