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# Wednesday, April 27, 2011

In this post I will describe a – in order to me – little strange behavior in Caliburn Micro ( CM ) that I discovered in my learning by doing sessions. So the scenario is the following, I have an application with a Main model acting as a screen conductor. The conduced screen are visualized as a classical tabbed application. The exercise goal is to define a visual command on the main view and route it to the proper active item, that is I think a quite common scenario. Let me clarify what I want to achieve with an image:


The TabModel class is actually the model connected to the single tab screen. Lets try to do by just naming conventions:

<Button Grid.Row="0" x:Name="Save"  >
                    <Image Source="assets/disk.png"/>


Well, it does not work automatically: CM wire just the MainModel, so we need to explicitly re-target the action on the Active child:

<Button Grid.Row="0" x:Name="Save"  cl:Action.TargetWithoutContext="{Binding Path=ActiveItem}">
                    <Image Source="assets/disk.png"/>
Unfortunately message is not routed yet. Let’s try to define the message handler in the main model:
class MainWindowModel:Conductor<object>.Collection.OneActive
       public MainWindowModel()
           Items.Add(new TabModel("Tab 1"));
           Items.Add(new TabModel("Tab 2"));
           Items.Add(new TabModel("Tab 3"));

       public void Save()
Well, it works !

This is because CM creates the poper handler in the main model, so it can route it when we re-target the handler. Since this is probably not the desired behavior, it is probably better to use this strategy instead:


<Button Grid.Row="0" x:Name="Save"  
cl:Message.Attach="[Event Click] = [Action Save()]"  
cl:Action.TargetWithoutContext="{Binding Path=ActiveItem}">
                    <Image Source="assets/disk.png"/>
By doing this we leave the naming convention strategy, and we explictly declare what we want to do, is better to avoid unpredictable behavior :)
If you are interested in the code for reproducing this check this issue.
Wednesday, April 27, 2011 4:59:28 PM (GMT Daylight Time, UTC+01:00)  #    Comments [0] - Trackback
Caliburn | WPF

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