在C ++ CLI中创建公共字符串

Question

I have 2 classes. I use System::Speech::recognition in C++/CLI. Now, I have the event handler at the end:

recognizer->SpeechRecognized += gcnew EventHandler<SpeechRecognizedEventArgs^>(sre_SpeechRecognized);

I also have the callback function:

void sre_SpeechRecognized(Object^ sender, SpeechRecognizedEventArgs^ e)
{
    // Do something
}

This throws me an Error:

Invalid Delegate initializer -- Function is no Member of a managed-class

Any idea why, and any idea how to fix it?

And another (related) question:

sre_SpeechRecognized() should assign the result value to a String variable.

Now: That string variable is declared in the same class: public: String^ res_SR = "" and C++ CLI hates me for that aswell. (Somehow I don't have std::string , only System::String ...)

Any idea on how to fix those 2 problems?

EDIT (In case my code snippet with the error in it helps):

ref class tsapi
{
    void recogn_speech() {
        SpeechRecognizer^ recognizer = gcnew SpeechRecognizer();

        Choices^ commands_vc = gcnew Choices();
        commands_vc->Add(gcnew array<String^> { "Move", "To" });

        GrammarBuilder^gb = gcnew GrammarBuilder();
        gb->Append(commands_vc);

        Grammar^ g = gcnew Grammar(gb);
        recognizer->LoadGrammar(g);

        // Register Event
        recognizer->SpeechRecognized += gcnew EventHandler<SpeechRecognizedEventArgs^>(sre_SpeechRecognized);
    }

    void sre_SpeechRecognized(Object^ sender, SpeechRecognizedEventArgs^ e)
    {
        String^ res = e->Result->Text->ToString();
    }
};

Answer 1

.Net doesn't have the concept of 'global functions'. Everything must be contained in a class. The C++/CLI compiler will take some methods & variables that look like globals, and stick them as static members in a special class, but apparently not everything. Take the code where you're doing recognizer->SpeechRecognized += ... , stick it in a class ( ref class , so it's a managed class), and put sre_SpeechRecognized in that class as well.

For the string assignment error, you need to move the assignment from the class definition into a constructor. Like C++, C++/CLI doesn't allow instance variables to be assigned in the class definition. However, I would consider leaving off the explicit assignment: Since you're assigning the empty string, consider just leaving the field as nullptr , which .Net ensures by default.