RelayCommand.cs

using System.Windows.Input;

namespace DeadDailyDose;

/// <summary>
/// Simple ICommand implementation for MVVM button binding.
/// </summary>
public class RelayCommand : ICommand
{
    private readonly Action<object?> _execute;
    private readonly Predicate<object?>? _canExecute;

    /// <summary>Creates a command that can always execute.</summary>
    public RelayCommand(Action<object?> execute) : this(execute, null) { }

    /// <summary>Creates a command with optional canExecute predicate.</summary>
    public RelayCommand(Action<object?> execute, Predicate<object?>? canExecute)
    {
        _execute = execute ?? throw new ArgumentNullException(nameof(execute));
        _canExecute = canExecute;
    }

    /// <inheritdoc />
    public bool CanExecute(object? parameter) => _canExecute == null || _canExecute(parameter);

    /// <inheritdoc />
    public void Execute(object? parameter) => _execute(parameter);

    /// <inheritdoc />
    public event EventHandler? CanExecuteChanged
    {
        add => CommandManager.RequerySuggested += value;
        remove => CommandManager.RequerySuggested -= value;
    }
}