WPF / XAML / MVVM - Set state of checkboxes based on conditions

Question

I am a traditional MVC programmer that just started using MVVM and I do not know how I would program the below scenario the MVVM-way. I probably need multi binding, but can someone please help me and write that code for me? I've spend hours trying to achieve this, but I just don't know how to do it...

Btw, I know how to set the values from my settings file in XAML, but don't know how to write the other logic, EG:

IsEnabled="{Binding Source={x:Static p:Settings.Default}, Path=Pref_QuickProcess}"

This is my scenario:

I have a simple preferences screen with two checkboxes:

□ Quick process (value is set from Settings.Default.Pref_QuickProcess)

□ Upload to youtube (value is set from Settings.Default.Pref_UploadToYoutube)

The following conditions apply:

If "Quick process" is true, "Upload to youtube" should always be set to false and must be disabled.
If "Quick process" is false, "Upload to youtube" should be enabled.

These are the only options:

This is my XAML:

This is my code behind:

public partial class PreferencesWindow : Window
{
    public PreferencesWindow()
    {
        InitializeComponent();

        chkQuickProcess.IsChecked = Settings.Default.Pref_QuickProcess;
        chkUploadToYoutube.IsChecked = Settings.Default.Pref_UploadToYoutube;

        ConfigureCheckboxes();

        chkQuickProcess.Click -= ChkQuickProcess_Click;
        chkQuickProcess.Click += ChkQuickProcess_Click;
    }

    private void ChkQuickProcess_Click(object sender, RoutedEventArgs e)
    {
        ConfigureCheckboxes();
    }

    void ConfigureCheckboxes()
    {
        if (chkQuickProcess.IsChecked.HasValue)
        {
            var isChecked = chkQuickProcess.IsChecked.Value;

            if (isChecked)
            {
                chkUploadToYoutube.IsChecked = false;
                chkUploadToYoutube.IsEnabled = false;
            }
            else
            {
                chkUploadToYoutube.IsEnabled = true;
            }
        }
    }

    protected override void OnClosing(CancelEventArgs e)
    {
        Settings.Default.Pref_QuickProcess = chkQuickProcess.IsChecked ?? false;
        Settings.Default.Pref_UploadToYoutube = chkUploadToYoutube.IsChecked ?? false;
        Settings.Default.Save();

        base.OnClosing(e);
    }
}

How do I get rid of my code behind, and get the same result in XAML with things like data triggers, converters, multi binding?

Edit: I think I do not necessarily need a viewmodel with setters to implement this logic, and do it with data triggers ? / multi binding ? instead. But maybe that is not possible?

user_1136211 · Answer

You probably don't need a view model just to set a few properties in the Settings class that have a certain interdependence. The following XAML should do most or perhaps all of what you are describing.

When the first Checkbox is checked, the IsChecked and IsEnabled properties of the second Checkbox are set to false. However, the Settings.Default.Pref_UploadToYoutube property value is not changed. Not sure if this is strictly required.

By default, the second CheckBox's IsChecked property is bound to Pref_UploadToYoutube via a Style Setter. A DataTrigger on the Pref_QuickProcess property replaces the Binding and sets IsChecked and IsEnabled to false.

Also note the new Binding Path syntax for binding to static properties.

You may also simplify the Settings properties binding paths by assigning the Settings.Default instance once to the DataContext of the StackPanel parent of the CheckBoxes:

WPF / XAML / MVVM - Set state of checkboxes based on conditions

1 Answers