Starts a synchronous speech recognition operation.

These methods perform a single, synchronous recognition operation. The recognizer performs this operation against its loaded and enabled speech recognition grammars.

During a call to this method, the recognizer can raise the following events:

• SpeechDetected. Raised when the recognizer detects input that it can identify as speech.

• SpeechHypothesized. Raised when input creates an ambiguous match with one of the active grammars.

• SpeechRecognitionRejected or SpeechRecognized. Raised when the recognizer finalizes a recognition operation.

The recognizer does not raise the RecognizeCompleted event when using one of the Recognize()()()() methods.

The Recognize methods return a RecognitionResult object, or nullNothingnullptrunita null reference (Nothing in Visual Basic) if the operation is not successful.

A synchronous recognition operation can fail for the following reasons:

• Speech is not detected before the timeout intervals expire for the BabbleTimeout or InitialSilenceTimeout properties, or for the initialSilenceTimeout parameter of the Recognize(TimeSpan) method.

• The recognition engine detects speech but finds no matches in any of its loaded and enabled Grammar objects.

To modify how the recognizer handles the timing of speech or silence with respect to recognition, use the BabbleTimeout, InitialSilenceTimeout, EndSilenceTimeout, and EndSilenceTimeoutAmbiguous properties.

The SpeechRecognitionEngine must have at least one Grammar object loaded before performing recognition. To load a speech recognition grammar, use the LoadGrammar or LoadGrammarAsync method.

To perform asynchronous recognition, use one of the RecognizeAsync methods.

Reference