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// This visitor implementation attemps to make the best of both worlds, between C#'s functional features and compile-time safety.
// Using extension methods as visitors makes it a runtime error for there not to be an equivalent visitor for every subclass of the element hierarchy.
// This approach ensures compile-time safety, while minimizing boilerplate. It's a step closer to the ideal of "if it compiles, it works".

using System;

Room room = new Bathroom(10);

RoomVisitor visitorPrintSurface = new(
    bathroom => Console.WriteLine($"Surface of bathroom: {bathroom.Surface}"),

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    public static bool IsInDirectory(this FileInfo file, DirectoryInfo directory) => file.Directory?.IsInDirectory(directory) ?? false;

    [SuppressMessage("Globalization", "CA1309", Justification = "Path comparison")]
    public static bool IsInDirectory(this DirectoryInfo path, DirectoryInfo directory)
        => path.Parent != null && (path.Parent.FullName.Equals(directory.FullName, StringComparison.InvariantCultureIgnoreCase) || path.Parent.IsInDirectory(directory));

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/// <typeparam name="TSender">The type of the source of the event.</typeparam>
/// <typeparam name="TEventArgs">The type of event data generated by the event.</typeparam>
/// <remarks>Type-safe variation from <see cref="EventHandler{TEventArgs}"/>.</remarks>
/// <inheritdoc cref="EventHandler{TEventArgs}"/>
[Serializable]
[SuppressMessage("Naming", "CA1711", Justification = "Type-safe event handler pattern")]
public delegate void TypeEventHandler<TSender, TEventArgs>(TSender sender, TEventArgs e);

/// <typeparam name="TSender">The type of the source of the event.</typeparam>
/// <remarks>Type-safe variation from <see cref="EventHandler"/>.</remarks>

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    private static void EnsureAdminPrivileges()
    {
        if (new WindowsPrincipal(WindowsIdentity.GetCurrent()).IsInRole(WindowsBuiltInRole.Administrator))
        {
            return;
        }
        ProcessStartInfo processInfo = new(Environment.ProcessPath.NotNull())
        {
            UseShellExecute = true,
            Verb = "runas"

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    public static async Task WithTimeout(this Task task, TimeSpan timeout)
    {
        CancellationTokenSource cts = new();
        if (task == await Task.WhenAny(task, Task.Delay(timeout, cts.Token)))
        {
            cts.Cancel();
        }
        else
        {
            throw new TimeoutException();

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<TextBlock>
    <TextBlock.Text>
        <MultiBinding StringFormat="{}{0:F0}x{1:F0}">
            <Binding ElementName="window" Path="ActualWidth" />
            <Binding ElementName="window" Path="ActualHeight" />
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>

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public static void EreaseSelection(this ICollectionView collectionView) => collectionView.MoveCurrentToPosition(-1);

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using System.Globalization;
using System.Windows.Data;

/// <summary>A converter based on equality comparisons between the value and the parameter.</summary>
public sealed class EqualsConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        => Equals(value, parameter);

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)

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public sealed class Ref<T>
{
    public Ref(T value) => Value = value;
    public T Value { get; set; }
    public static implicit operator T(Ref<T> @ref) => @ref.Value;
}

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    public static IEnumerable<T> FindVisualChildren<T>(this DependencyObject depObj) where T : DependencyObject
    {
        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
        {
            var child = VisualTreeHelper.GetChild(depObj, i);
            if (child is T t)
            {
                yield return t;
            }
            foreach (T childOfChild in FindVisualChildren<T>(child))