SpeechRecognitionEngine.RequestRecognizerUpdate Method ()


Requests that the recognizer pauses to update its state.

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

public void RequestRecognizerUpdate()

When the recognizer generates the RecognizerUpdateReached event, the UserToken property of the RecognizerUpdateReachedEventArgs is null.

To provide a user token, use the RequestRecognizerUpdate or RequestRecognizerUpdate method. To specify an audio position offset, use the RequestRecognizerUpdate method.

The following example shows a console application that loads and unloads Grammar objects. The application uses the RequestRecognizerUpdate method to request the speech recognition engine to pause so it can receive an update. The application then loads or unloads a Grammar object.

At each update, a handler for RecognizerUpdateReached event writes the name and status of the currently loaded Grammar objects to the console. As grammars are loaded and unloaded, the application first recognizes the names of farm animals, then the names of farm animals and the names of fruits, then only the names of fruits.

using System;
using System.Speech.Recognition;
using System.Collections.Generic;
using System.Threading;

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

      // Initialize an in-process speech recognition engine and configure its input.
      using (recognizer = new SpeechRecognitionEngine(new System.Globalization.CultureInfo("en-US")))

        // Create the first grammar - Farm.
        Choices animals = new Choices(new string[] { "cow", "pig", "goat" });
        GrammarBuilder farm = new GrammarBuilder(animals);
        Grammar farmAnimals = new Grammar(farm);
        farmAnimals.Name = "Farm";

        // Create the second grammar - Fruit.
        Choices fruit = new Choices(new string[] { "apples", "peaches", "oranges" });
        GrammarBuilder favorite = new GrammarBuilder(fruit);
        Grammar favoriteFruit = new Grammar(favorite);
        favoriteFruit.Name = "Fruit";

        // Attach event handlers.
        recognizer.SpeechRecognized +=
          new EventHandler<SpeechRecognizedEventArgs>(recognizer_SpeechRecognized);
        recognizer.RecognizerUpdateReached +=
          new EventHandler<RecognizerUpdateReachedEventArgs>(recognizer_RecognizerUpdateReached);
        recognizer.SpeechRecognitionRejected +=
          new EventHandler<SpeechRecognitionRejectedEventArgs>(recognizer_SpeechRecognitionRejected);

        // Load the Farm grammar.

        // Start asynchronous, continuous recognition.
        Console.WriteLine("Starting asynchronous, continuous recognition");
        Console.WriteLine("  Farm grammar is loaded and enabled.");

        // Pause to recognize farm animals.

        // Request an update and load the Fruit grammar.

        // Request an update and unload the Farm grammar.

      // Keep the console window open.
      Console.WriteLine("Press any key to exit...");

    // At the update, get the names and enabled status of the currently loaded grammars.
    public static void recognizer_RecognizerUpdateReached(
      object sender, RecognizerUpdateReachedEventArgs e)
      Console.WriteLine("Update reached:");

      string qualifier;
      List<Grammar> grammars = new List<Grammar>(recognizer.Grammars);
      foreach (Grammar g in grammars)
        qualifier = (g.Enabled) ? "enabled" : "disabled";
        Console.WriteLine("  {0} grammar is loaded and {1}.",
        g.Name, qualifier);

    // Write the text of the recognized phrase to the console.
    static void recognizer_SpeechRecognized(object sender, SpeechRecognizedEventArgs e)
      Console.WriteLine("    Speech recognized: " + e.Result.Text);

    // Write a message to the console when recognition fails.
    static void recognizer_SpeechRecognitionRejected(object sender, SpeechRecognitionRejectedEventArgs e)
      Console.WriteLine("    Recognition attempt failed");

.NET Framework
Available since 3.0
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