Question

In a c# assembly I’ve got a global prism CompositeCommand to subscribe to like this:

private static readonly CompositeCommand __myCommand = new CompositeCommand();

public static CompositeCommand MyCommand
{
  get { return _myCommand; }
}

From c# I can subscribe to this command using:

[...].MyCommand.RegisterCommand(new DelegateCommand<MyClass>((c) => c.Something()));

My problem: I need to subscribe to the command from managed c++, and I got no idea how the function signature needs to be to be used in DelegateCommand. Most of the time I get errors like:

error C2664: ‘Microsoft::Practices::Prism::Commands::DelegateCommand::DelegateCommand(System::Action ^)’: conversion of parameter 1 from ‘void (__clrcall *)(MyNameSpace::MyClass ^)’ in ‘System::Action ^’ not possible.

How do I subscribe to a c# command? Or is there some other way to listen to an event (I can replace the CompositeCommand with something different).

Thanks!

Answer 1

I’m going to assume that you’re using managed C++ – anything else, and there’s bigger issues to worry about.

It looks like you’re getting linking errors to your C# type. As such, I don’t think the issue is related to any problems with Prism. In order for the C++ managed compiler to link to your C# assembly, you need to produce the C# assembly with an XML documentation file (see the Build tab in your properties). Is that enabled in your project?

I used the following as a very simple proof of concept, where TestObject is defined in the C# assembly referenced by the C++ DLL. This compiled without any issues.

Header file:

 void __clrcall CommandCallback(Project::Infrastructure::TestObject^ param);

public ref class ManagedModule : IModule
{
public:
    ManagedModule();

     virtual void __clrcall Initialize();

private:
};

Implementation:

ManagedDLL::ManagedModule::ManagedModule()
{

}

void __clrcall ManagedDLL::ManagedModule::Initialize()
{
    Action<Project::Infrastructure::TestObject^>^ newAction = 
         gcnew Action<Project::Infrastructure::TestObject^>(&CommandCallback);
    DelegateCommand<Project::Infrastructure::TestObject^>^ newCommand = 
         gcnew DelegateCommand<Project::Infrastructure::TestObject^>(newAction);
    Project::Infrastructure::Commands::ApplicationExitCommand->RegisterCommand(newCommand);

    return;
}

void __clrcall CommandCallback(Project::Infrastructure::TestObject^ param)
{
    return;
}