SpeechRecognitionEngine.RecognizeAsyncCancel Method ()

 

Terminates asynchronous recognition without waiting for the current recognition operation to complete.

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

public void RecognizeAsyncCancel()

This method immediately finalizes asynchronous recognition. If the current asynchronous recognition operation is receiving input, the input is truncated and the operation completes with the existing input. The recognizer raises the RecognizeCompleted or EmulateRecognizeCompleted event when an asynchronous operation is canceled, and sets the Cancelled property of the RecognizeCompletedEventArgs to true. This method cancels asynchronous operations initiated by the RecognizeAsync and EmulateRecognizeAsync methods.

To stop asynchronous recognition without truncating the input, use the RecognizeAsyncStop method.

The following example shows part of a console application that demonstrates the use of the RecognizeAsyncCancel method. The example creates and loads a speech recognition grammar, initiates a continuing asynchronous recognition operation, and then pauses 2 seconds before it cancels 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 cancel the recognition operation.
        Thread.Sleep(TimeSpan.FromSeconds(2));
        recognizer.RecognizeAsyncCancel();

        // 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
Available since 3.0
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