How to implement a 'wait' state when using multi-threading in C# - multithreading

Question

I have a class that I am applying multi-threading to. I would like to only allow 1 thread to 'startSpeaking()' at one time. Here is my attempt:
class VoiceEffect
{
SpeechSynthesizer reader = new SpeechSynthesizer();
static readonly object _locker = new object();
public void createVoiceThread(string str)
{
Thread voicethread = new Thread(() => startSpeaking(str)); // Lambda Process
voicethread.IsBackground = true;
voicethread.Start();
}
public void startSpeaking(string str)
{
lock (_locker)
{
reader.Rate = -2; // Voice effects.
reader.Volume = 100;
reader.Speak(str);
}
}
}
I am also calling createVoiceThread() method from another class. It is called by a similar convention in another class. E.g.
class Program
{
static void Main(string[] args)
{
VoiceEffect ve = new VoiceEffect();
string text = "Hello world, how are you today? I am super-duper!!";
for( int i=0 ; i < 10 ; i++ )
{
ve.createVoiceThread(text);
ve.startSpeaking(text);
Thread.Sleep(1000);
}
}
}
My question is how can I modify this program so that when startSpeaking() is called by any thread, that it only plays a single speech pattern at a time.

Answer 1

I know this question's old as hell, but if I'm understanding your question correctly (that you want all the speech done sequentially, as if it were done on a single thread) you can do something like this:
static class VoiceEffect
{
SpeechSynthesizer reader = new SpeechSynthesizer();
private volatile bool _isCurrentlySpeaking = false;
/// <summary>Event handler. Fired when the SpeechSynthesizer object starts speaking asynchronously.</summary>
private void StartedSpeaking(object sender, SpeakStartedEventArgs e)
{ _isCurrentlySpeaking = true; }
/// <summary>Event handler. Fired when the SpeechSynthesizer object finishes speaking asynchronously.</summary>
private void FinishedSpeaking(object sender, SpeakCompletedEventArgs e)
{ _isCurrentlySpeaking = false; }
private VoiceEffect _instance;
/// <summary>Gets the singleton instance of the VoiceEffect class.</summary>
/// <returns>A unique shared instance of the VoiceEffect class.</returns>
public VoiceEffect GetInstance()
{
if(_instance == null)
{ _instance = new VoiceEffect(); }
return _instance;
}
/// <summary>
/// Constructor. Initializes the class assigning event handlers for the
/// SpeechSynthesizer object.
/// </summary>
private VoiceEffect()
{
reader.SpeakStarted += new EventHandler<SpeakStartedEventArgs>(StartedSpeaking);
reader.SpeakCompleted += new EventHandler<SpeakCompletedEventArgs>(FinishedSpeaking);
}
/// <summary>Speaks stuff.</summary>
/// <param name="str">The stuff to speak.</param>
public void startSpeaking(string str)
{
reader.Rate = -2; // Voice effects.
reader.Volume = 100;
// if the reader's currently speaking anything,
// don't let any incoming prompts overlap
while(_isCurrentlySpeaking)
{ continue; }
reader.SpeakAsync(str);
}
/// <summary>Creates a new thread to speak stuff into.</summary>
/// <param name="str">The stuff to read.</param>
public void createVoiceThread(string str)
{
Thread voicethread = new Thread(() => startSpeaking(str)); // Lambda Process
voicethread.IsBackground = true;
voicethread.Start();
}
}
This gives you a singleton class that will manage all threads, and all threads will share the _isCurrentlySpeaking variable, which will mean that no speech prompts will ever overlap each other since they'll all have to wait until the variable is cleared before speaking. What I cannot guarantee is the order the prompts will be read (i.e., take control of the message-processing queue), if you submit multiple prompts to the queue while there's a prompt being spoken aloud already. Either way, this should pretty much work.

Answer 2

Your question isn't clear, but you have a single lock variable (_locker) which is static - that means only one thread can ever be executing startSpeaking at a time. It's not clear whether you're trying to make threads wait for each other, or whether your question is because you don't want them to wait for each other.
Either way, having a single static lock used like this is distinctly dubious, IMO. If you can really only effectively have one useful instance of this class, consider making it a singleton. (Generally not nice in terms of design.) If it's fine to have multiple independent instances, then make them independent by making the _locker variable an instance variable.
(I'd also strongly advise you to start following .NET naming conventions.)