Caliburn Micro 'Enter' Key Event

Question

I am attempting to bind an event with Caliburn Micro and I am having some issues getting the right messages to the method. I would like to add the ability to press the \'Ent

Answer 1

If using keyeventargs as parameter type , and it gives u back null ,then look at this: You propably using System.Windows.Forms.KeyEventArgs and KeyEventArgs, as parameter type is refering to this, try with System.Windows.Input.KeyEventArgs (it works for me).

public void ExecuteFilterView(System.Windows.Input.KeyEventArgs context)
{
     if(context.Key==System.Windows.Input.Key.Return)
     {
         //action here
     }      
}

Answer 2

Just threw a test together, both of these work for me:

Using full syntax:

    <TextBox Name="Threshold"                     
          Margin="5"
          Grid.Column="1">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="KeyDown">
                <cal:ActionMessage MethodName="ExecuteFilterView">
                    <cal:Parameter Value="$executionContext"/>
                </cal:ActionMessage>
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </TextBox>

Using CM syntax (prefer this as it's way more readable)

    <TextBox Name="Threshold"                     
          Margin="5"
          Grid.Column="1"
          cal:Message.Attach="[Event KeyDown] = [Action ExecuteFilterView($executionContext)]" />            

This was the test VM:

public class MainWindowViewModel
{
    public void ExecuteFilterView(ActionExecutionContext context)
    { 
        // This method is hit and the context is present and correct
    }
}

Can you post your full code - are you sure you have the framework setup correctly? (have you followed the getting started example?

http://caliburnmicro.codeplex.com/wikipage?title=Basic%20Configuration%2c%20Actions%20and%20Conventions&referringTitle=Documentation

Edit:

Ok after your clarification I can give you some examples of how to do this - I'll tell you my personal preference and why, but choose the one that fits you best

1. Using ActionExecutionContext and casting the eventargs:

    cal:Message.Attach="[Event KeyDown] = [Action ExecuteFilterView($executionContext)]"

    public void ExecuteFilterView(ActionExecutionContext context)
    {
        var keyArgs = context.EventArgs as KeyEventArgs;

        if (keyArgs != null && keyArgs.Key == Key.Enter)
        {
            // Do Stuff
        }
    }

2. Using EventArgs directly

    cal:Message.Attach="[Event KeyDown] = [Action ExecuteFilterView($eventArgs)]"

    public void ExecuteFilterView(KeyEventArgs keyArgs)
    {
        if (keyArgs.Key == Key.Enter)
        {
            // Do Stuff
        }
    }

3. My personal fave, creating your own SpecialValues dictionary entry:

In your Bootstrapper.Configure method...

MessageBinder.SpecialValues.Add("$pressedkey", (context) =>
{
    // NOTE: IMPORTANT - you MUST add the dictionary key as lowercase as CM
    // does a ToLower on the param string you add in the action message, in fact ideally
    // all your param messages should be lowercase just in case. I don't really like this
    // behaviour but that's how it is!
    var keyArgs = context.EventArgs as KeyEventArgs;

    if (keyArgs != null)
        return keyArgs.Key;

    return null;
});

Your action:

cal:Message.Attach="[Event KeyDown] = [Action ExecuteFilterView($pressedKey)]"

And the code:

public void ExecuteFilterView(Key key)
{
    if (key == Key.Enter)
    {
        // Do Stuff
    }
}

The reason this is my favourite? It means that your VM just receives the value you want (most of the time you don't care about a lot of the other parameters) and you don't need to know how to or bother to cast the eventargs - you can just operate on the value. Obviously use whatever is best for you

It's also worth noting, that if you have other types of controls that subclass KeyEventArgs this will work for them. If they don't subclass KeyEventArgs but they still return a value of type Key this will still work too as you can just add another cast to the delegate if the first one fails:

e.g.

MessageBinder.SpecialValues.Add("$pressedkey", (context) =>
{
    var keyArgs = context.EventArgs as KeyEventArgs;

    if (keyArgs != null)
        return keyArgs.Key;

    // Ok so it wasn't KeyEventArgs... check for some other type - maybe a 3rd party implementation
    var thirdPartyKeyArgs = context.EventArgs as ThirdPartyKeyArgs;

    if (thirdPartyKeyArgs != null)
        return thirdPartyKeyArgs.KeyProperty;

    return null;
});