C＃Singleton暴露于MS Word Interop加载项

Question

I've been having an issue and only recently pinpointed the following as being the cause (was troubleshooting a symptom until now). Basically, I have a Solution that has a WPF application project (the startup), a bunch of assemblies (Model, ModelView, etc), and a Word VSTO Add-in. The ViewModel and the Word Add-in both compose one of the Models, which for this stage of development, I have made a Singleton.

The Viewmodel instantiates the model in its constructor using

ModelSingleton mod =  ModelSingleton.Instance;

The addin does the same thing on ThisAddIn_Startup() method.

Model code:

private static volatile ModelSingleton instance;
private static object syncRoot = new Object();

private ModelSingleton()
{
}

public static ModelSingleton Instance
{
    get
    {
        lock (syncRoot)
        {
            if (instance == null)
            {
                 instance = new ModelSingleton();
            }
        }
        return instance;
    }
}

I want the Word Addin to capture highlighted text and pass it to my model, which then generates its own event that the Viewmodel is subbed to.

My issue is that both the addin and the viewmodel are creating separate instances of what is supposed to be a Singleton. The highlighted text is passed to one Singleton but no event is generated because the ViewModel subscribed to the event in another instance.

I'm a newb to Interop and COM; I would expect a singleton to only be instantiated once. Are there two separate runtimes or something going on here (apparently, the VSTO and the WPF are both executables which means they cannot directly share data)? How do I make the Singleton a true Singleton? And if that's impossible, how would you pass highlighted text (and metadata) from MS Word to your proprietary app?

Answer 1

I think you are trying to do this:

public static ModelSingleton Instance
{
    private static ModelSingleton instance = null;
    private static readonly object syncRoot = new Object();

    private ModelSingleton()
    {
    }
    get
    {
        lock (syncRoot)
        {
            if (instance == null)
            {
                 instance = new ModelSingleton();
            }
        }
    return instance;
    }
}

this will give you thread safety without any deadlocks