void engine_SpeechRecognized(object sender, SpeechRecognizedEventArgs e)
{
    if (this.SpeechRecognized != null)
    {
       this.SpeechRecognized(this, new RecognizedResultEventArgs
            {
                Text = e.Result.Text,
                Alternates = new ReadOnlyCollection<string>(e.Result.Alternates.Select(p => p.Text).ToList())
            });
    }
}

private const int grammarId = 10;
 private bool speechInitialized = false;
 private SpeechLib.SpSharedRecoContext objRecoContext;
 private SpeechLib.ISpeechRecoGrammar grammar;
 private SpeechLib.ISpeechGrammarRule ruleListItems;

// 初始化识别上下文
private void InitializeSpeech(List<string> userKeyWords = null, bool isUseSystemGrammar = false)
    {
        try
        {
            // First of all, let's create the main reco context object. 
            // In this sample, we are using shared reco context. Inproc reco
            // context is also available. Please see the document to decide
            // which is best for your application.
            objRecoContext = new SpeechLib.SpSharedRecoContext();

            // Then, let's set up the event handler. We only care about
            // Hypothesis and Recognition events in this sample.
            objRecoContext.Hypothesis += new
                _ISpeechRecoContextEvents_HypothesisEventHandler(
                RecoContext_Hypothesis);

            objRecoContext.Recognition += new
                _ISpeechRecoContextEvents_RecognitionEventHandler(
                RecoContext_Recognition);

            objRecoContext.AudioLevel += new _ISpeechRecoContextEvents_AudioLevelEventHandler(objRecoContext_AudioLevel);

            objRecoContext.EventInterests = SpeechRecoEvents.SREAllEvents;

            // Now let's build the grammar.               
            grammar = objRecoContext.CreateGrammar(grammarId);
            ruleListItems = grammar.Rules.Add("ListItemsRule",
               SpeechRuleAttributes.SRATopLevel | SpeechRuleAttributes.SRADynamic, 1);

            RebuildGrammar(userKeyWords, isUseSystemGrammar);

            // Now we can activate the top level rule. In this sample, only 
            // the top level rule needs to activated. The ListItemsRule is 
            // referenced by the top level rule.
            grammar.CmdSetRuleState("ListItemsRule", SpeechRuleState.SGDSActive);
            speechInitialized = true;
        }
        catch (Exception e)
        {
            Loger.LogErr(e);
        }
    }

// 事件响应，这里会有一个异常
public void RecoContext_Recognition(int StreamNumber, object StreamPosition, SpeechRecognitionType RecognitionType, ISpeechRecoResult Result)
    {
        ISpeechPhraseProperty oItem;

        oItem = Result.PhraseInfo.Properties.Item(0);

        if ((System.Decimal)Result.PhraseInfo.GrammarId == grammarId)
        {
            if (this.SpeechRecognized != null)
            {
                RecognizedResultEventArgs e = new RecognizedResultEventArgs();
                e.Text = oItem.Name;

                // The following code throws an exception
                ISpeechPhraseAlternates alternates = Result.Alternates(10);
                List<string> s = new List<string>();
                foreach (ISpeechPhraseAlternate item in alternates)
                {
                    s.Add(item.RecoResult.PhraseInfo.Properties.Item(0).Name);
                }
                e.Alternates = new ReadOnlyCollection<string>(s);

                this.SpeechRecognized(this, e);
            }
        }
    }