SimpleToDoList - CompiledBinding fails, ReflectionBinding works

[descenteer]

So, I'm rather new to data binding and I'm trying to figure out why a particular thing is failing while I'm working through the SimpleToDoList sample tutorial.

When I implement this section of step 4:

<Button Command="{Binding #Root.((vm:MainViewModel)DataContext).RemoveItemCommand}" CommandParameter="{Binding .}" Grid.Column="1">

It compiles and runs, but I get a System.ArgumentException at when I attempt to create a new item. Change it around to use ReflectionBinding like so:

<Button Grid.Column="1" Command="{Binding #Root.DataContext.RemoveItemCommand}" CommandParameter="{Binding .}">

And it works as expected. I've poked around for a couple of hours - and am continuing to do so - but has anybody got any directions I should chase to figure out why this is happening?

[timunie]

Please show me what you have so far. Best if you can upload a minimal sample here (without obj and bin folder).