WPF MVVM event to command - invoke command based on event args

Question

I have a WPF app which uses DevExpress controls and MVVM with PRISM.
I'm using DockLayoutManager's 'DockOperationCompleted' event to invoke a command on my view model like this:

    <dxd:DockLayoutManager x:Name="dockContainer">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="DockOperationCompleted">
                <i:InvokeCommandAction Command="{Binding DataContext.SaveLayoutCommand, ElementName=dockContainer}" />
            </i:EventTrigger>
        </i:Interaction.Triggers>
        <dxd:LayoutGroup/>
    </dxd:DockLayoutManager>

The purpose of the 'SaveLayoutCommand' command is to save the layout so it can be restored later in time.
The 'DockOperationCompleted' event is raised after a DockItem gets docked or closed (there are other cases but they are irrelevant).
The problem is that when I close the main window, the dock items in my DockLayoutManager are getting closed one by one and thus 'SaveLayoutCommand' gets invoked for every closed dock item and I don't want this to happen.
The 'DockOperationCompletedEventArgs' with which the event gets raised has a 'DockOperation' property which I can check agains, but I'm not sure where exactly should this code fit in.
What I am trying to achieve is that the command should be invoked only in one case - when the item is docked
My question is : is there a way to 'filter' when the command gets invoked based on the event's event args?

Thanks :)

score 3 · Answer 1 · answered Apr 24 '14 at 08:05

In addition to aKzenTs answer I want to point out that with DevExpress its rather easy to pass the event args to a command.

You should use EventToCommand from their MVVM library (PassEventArgsToCommand-Property). If you want to keep your viewmodel clean of DevExpress you can additionally use a Converter to transform the event args to an arbitrary object.

<dxmvvm:Interaction.Triggers>
    <dxmvvm:EventToCommand Command="{Binding YOURCOMMAND}"
                           EventName="THEEVENT"
                           EventArgsConverter="{StaticResource YOUREVENTARGSCONVERTER}"
                           PassEventArgsToCommand="true" />
</dxmvvm:Interaction.Triggers>

score 1 · Accepted Answer · edited May 23 '17 at 11:56

1

There is no builtin way to filter the events that are raised before invoking an action. You can however implement your own custom trigger action that does the filtering.

Unfortunately it's also not easy to access the event args and passing them to the command. See this question as a reference:

MVVM Passing EventArgs As Command Parameter

edited May 23 '17 at 11:56

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answered Mar 14 '13 at 15:42

aKzenT

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WPF MVVM event to command - invoke command based on event args

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