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Nitrox.Launcher/ViewModels/Abstract/ModalViewModelBase.cs

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+using System.Linq;
+using Avalonia;
+using Avalonia.Controls.ApplicationLifetimes;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using CommunityToolkit.Mvvm.Messaging;
+using HanumanInstitute.MvvmDialogs;
+using Nitrox.Launcher.Models;
+
+namespace Nitrox.Launcher.ViewModels.Abstract;
+
+/// <summary>
+///     Base class for (popup) dialog ViewModels.
+/// </summary>
+public abstract partial class ModalViewModelBase : ObservableValidator, IModalDialogViewModel, IMessageReceiver
+{
+    [ObservableProperty] private ButtonOptions? selectedOption;
+
+    bool? IModalDialogViewModel.DialogResult => (bool)this;
+
+    protected ModalViewModelBase()
+    {
+        // Always run validation first so HasErrors is set (i.e. trigger CanExecute logic).
+        ValidateAllProperties();
+    }
+
+    public static implicit operator bool(ModalViewModelBase self)
+    {
+        return self is { HasErrors: false } and not { SelectedOption: null or ButtonOptions.No };
+    }
+
+    /// <summary>
+    ///     Closes the dialog window. By default, sets the dialog result as cancelled.
+    /// </summary>
+    /// <param name="buttonOptions">The dialog result to set before closing.</param>
+    [RelayCommand]
+    public void Close(ButtonOptions? buttonOptions = null)
+    {
+        if (buttonOptions != null)
+        {
+            SelectedOption = buttonOptions;
+        }
+        ((IClassicDesktopStyleApplicationLifetime)Application.Current?.ApplicationLifetime)?.Windows.FirstOrDefault(w => w.DataContext == this)?.CloseByUser();
+    }
+
+    public virtual void Dispose()
+    {
+        WeakReferenceMessenger.Default.UnregisterAll(this);
+    }
+}