Caliburn.Micro messes up the conventional binding of a Button? - caliburn.micro

Question

I have just fired up a WPF project and I want to use Caliburn.Micro.
I have a button
<Button Content="Button" Name="AppendData">
and in my ViewModel I have a method void AppendData(){..}
It doesn't work! There is no binding between the two! But when I do this
<Button Content="Button" cal:Message.Attach="AppendData()">
it suddenly works. What can be the cause of this?
Edit:
I have created a test application where the conventions doesn't work: http://ge.tt/8sNsu201?c
You can make it work, by replacing the controls in MyView with
<Button cal:Message.Attach="SetText()" Content="Button" HorizontalAlignment="Left" Margin="106,153,0,0" VerticalAlignment="Top" Width="75"/>
<Label Content="{Binding Text}" HorizontalAlignment="Left" Margin="124,104,0,0" VerticalAlignment="Top"/>

Answer 1

After taking a look at your source code, I noticed a major mistake which is causing all of this confusion:
public MyView()
{
InitializeComponent();
DataContext = new MyViewModel(); // SOURCE OF TROUBLE
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
}
In Caliburn.Micro you don't set the DataContext for your view manually like that, instead you let Caliburn.Micro use its conventions to find the appropriate view for your view-model, then it will bind the two together (by setting the view-model as the DataContext of the view), after that it will apply a number of conventions to make everything work correctly.
Explaining why using cal:MessageAttach() would work and directly using AppendData won't work would take a lot of explanation because it seems you don't know the basics of CM.
So I advise you to take a look at the documentation wiki first and go through the first 5 articles at least, then here is a hint that will help you discover why the first method worked and the second didn't:
Message Bubbling

Answer 2

Because this would expand the comments maximum length, I write it as an answer.
As you mentioned in your answer, doing DataContext = new MyViewModel() is a kind of code smell in CM. If you want to hook up it manually in your view, this would be the right way (view first). Check out the CM documentation regarding this one though, because I think there might be missing something:
var viewModel = new MyViewModel();
var view = this;
ViewModelBinder.Bind(viewModel, view, null);
You can accomplish this in the XAML of your view, either. Add the following into the UserControl tag of your view (view first, as well):
xmlns:cal="http://www.caliburnproject.org"
cal:Bind.Model="MyViewModel"
View model first would be done quite the same, in case you are not willing to use the default behavior you described in your answer:
xmlns:cal="http://www.caliburnproject.org"
cal:View.Model="MyViewModel"
I am not sure, but I think you have to add an explicitly named export contract to your view model, if you want to use View.Model or Bind.Model, but it might be it works without as well. Try it out:
[Export("MyViewModel", typeof(MyViewModel))]
public class MyViewModel : Screen
{
// ...
}
Design time views have nothing to do with view first or view model first though!
Design-time view support is accomplished as follows:
xmlns:cal="http://www.caliburnproject.org"
d:DataContext="{d:DesignInstance viewModels:MyViewModel, IsDesignTimeCreatable=True}"
cal:Bind.AtDesignTime="True"
I am currently not able to test all those things, so I hope there are not any mistakes!