Using eventtrigger without clicking - wpf

Question

I have a CheckBox that's set up like so:
<CheckBox x:Name="ViewTypeCheckbox" IsChecked="{Binding ViewType, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="Click">
<i:InvokeCommandAction Command="{Binding Refresh}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</CheckBox>
This functions as it's supposed to. When checked or unchecked by mouse click, the command is fired in the ViewModel.
You see the checkBox is databound to a bool property ("ViewType") that regularly turns from true to false and viseversa in response to user input.
The problem is I need the EventTrigger to fire when checked or unchecked by the ViewModel.
I've tried changing the "EventName" to "Checked", "IsChecked" and "UnChecked" but that doesn't seem to do anything.
Is there any additional code I need to implement? How would I get this to work?

Answer 1

You don't need Interaction.Triggers,
WPF provides support for commands out of the box.
Try simplifying your XAML by using a command attribute instead. It should resolve your issue.

Answer 2

If you need to call some code when the ViewTypeCheckbox.IsChecked changes its value, you can simply register an event handler to the PropertyChanged event of your view model (assuming it implements INotifyPropertyChanged), then call the code when the property ViewType changes:
myViewModel.PropertyChanged += new PropertyChangedEventHandler(onPropertyChanged);
...
private void onPropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName=="ViewType")
{
// Do your stuff here
// Ex. fire the Refresh Command
}
}
This can be done in the ViewModel class itself or whatever you need.
To complete the example I add a short implementation of INotifyPropertyChanged in the viewmodel class:
public class MyViewModel : INotifyPropertyChanged
{
...
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void RaisePropertyChanged(string propertyName)
{
var handler = PropertyChanged;
if (handler!=null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
...
// property definition to bind to ViewTypeCheckbox.IsChecked
private bool _viewType;
public bool ViewType
{
get { return _viewType; }
set
{
if (value != _viewType)
{
_viewType = value;
RaisePropertyChanged("ViewType");
}
}
}
}
Hope it helps

Answer 3

You don't need a trigger to execute your action. You can do it in the viewmodel when the property change.
public Boolean ViewType
{
get
{
return this.something;
}
set
{
this.something = value;
if (true == this.something)
{
this.Refresh();
}
}
}