WPF trigger from Settings.settings variable

Question

I added bool variable into my Settings.settings file to store user configuration preferences:

And in code behind i am changing this this way:

Properties.Settings.Default.autoCheckForUpdates = true;

Is it possible to add this bool var to my control trigger using XAML ?

I would recommend using a model in between, see: https://stackoverflow.com/questions/23648832/viewmodels-in-mvc-mvvm-seperation-of-layers-best-practices — Stefan, Mar 04 '18 at 08:39
Yes, create a `viewmodel` for your `xaml-view`, you can set the `BindingContext` from it's "code-behind". If your view interacts with your viewmodel, you can set your settings though that. It seems ike more effort but in the long run it is better to maintain. I could fix you an example if you like — Stefan, Mar 04 '18 at 08:52
Yes i will glad to see example, BTW i need to implement INotifyPropertyChanged as well ? — user2908206, Mar 04 '18 at 08:56

Clemens · Accepted Answer · 2018-03-04T09:51:54.393

3

The DataTrigger shown below works. You don't need a view model with property change notification, since the Settings class already implements INotifyPropertyChanged.

xmlns:properties="clr-namespace:YourAppNamespace.Properties"
...

<DataTrigger Binding="{Binding Path=(properties:Settings.Default).autoCheckForUpdates}"
             Value="True">
    <Setter .../>
</DataTrigger>

edited Mar 04 '18 at 09:51

answered Mar 04 '18 at 08:57

Clemens

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Can i have this example inside MenuItem please ? – user2908206 Mar 04 '18 at 08:58
In which MenuItem? You haven't shown any in your question. Just add this DataTrigger to the Triggers collection of a Style. – Clemens Mar 04 '18 at 09:00
Will it save the setting as well? – Stefan Mar 04 '18 at 09:02
@Stefan Why would it? It doesn't even change a setting. OP is asking about a trigger, not a TwoWay binding to a setting. – Clemens Mar 04 '18 at 09:04
I got this error: XamlParseException: Type reference cannot find type named '{http://schemas.microsoft.com/winfx/2006/xaml/presentation}Properties.Settings'. – user2908206 Mar 04 '18 at 09:50
You need to declare the Properties namespace in XAML, like `xmlns:properties="clr-namespace:YourAppNamespace.Properties"` – Clemens Mar 04 '18 at 09:51

Stefan · Answer 2 · 2018-03-04T09:05:46.260

As promised, the overkill version, which doesn't makes sense for your question but might help you out in another way: a simple viewmodel with INotifyPropertyChanged. I wil extend the example with some binding.

Your viewmodel:

public class SettingsViewModel : INotifyPropertyChanged
{
    private bool _autoUpdate;
    public SettingsViewModel()
    {
        //set initial value
        _autoUpdate = Properties.Settings.Default.autoCheckForUpdates;
    }

    public bool AutoCheckForUpdates 
    {
        get { return _autoUpdate; }
        set
        {
            if (value == _autoUpdate) return;
            _autoUpdate= value;
            Properties.Settings.Default.autoCheckForUpdates = value;
            Properties.Settings.Default.Save();
            OnPropertyChanged();
        }
    }

    //the INotifyPropertyChanged stuff
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

In the code behind of your XAML:

public SettingsWindow()
{
    InitializeComponent();
    this.DataContext = new SettingsViewModel();
}

Now, in your XAML, you can bind to this property, through a textbox for example:

<CheckBox IsChecked="{Binding AutoCheckForUpdates}"/>

WPF trigger from Settings.settings variable

2 Answers2