How do I make Calburn.Micro use my multi-parameter constructor?

When I have a View Model setup with an ImportingConstructor that takes a single parameter, the constructor is called and the screen is correctly shown. Example:

    [ImportingConstructor]
    public ShellViewModel(IEventAggregator eve开发者_JS百科nts)
    {
        events.Subscribe(this);
    }

However, based on examples from Caliburn.Micro, it seems I should be able to provide a different constructor with N parameters. Example:

    [ImportingConstructor]
    public ShellViewModel(LeftViewModel left, RightViewModel right, IEventAggregator events)
    {
        Left = left;
        Right = right;

        events.Subscribe(this);
    }

But this version of the constructor is never called in my sandbox. I have compiled and ran sample code from Caliburn.Micro that does this exact thing; calls a multiparameter constructor. (See Caliburn.Micro sample project "HelloEventAggregator")

Indeed - when I run my sandbox code (the second version) the constructor is not called, and a different ViewModel is selected as the initial display. But in the HelloEventAggregator sample their shellview model is constructed and displayed first.

What do I need to do to get Caliburn.Micro to call my multi-parameter constructor, and show the correct View?

The problem arrised because I had more than one view model set with

[Export(typeof(IShell))]

The export type should be whatever your [ImportingConstructor] is expecting, for that contract to be satisfied.

Example - ShellViewModel

[Export(typeof(IShell))]
public class ShellViewModel : PropertyChangedBase, IShell
{
    [ImportingConstructor]
    public ShellViewModel(LeftViewModel leftModel)
    {
        ...
    }
    ...
}

Example - LeftViewModel

[Export(typeof(LeftViewModel))]
public class LeftViewModel : PropertyChangedBase, IShell
{
    [ImportingConstructor]
    public LeftViewModel(IEventAggregator events)
    {
        events.Subscribe(this);
        ...
    }
    ...
}