Added checking for updates

ViewModels/RelayCommand.cs

@@ -0,0 +1,94 @@
+using System.Windows.Input;
+
+namespace MossyUpdater.ViewModels
+{
+    public class RelayCommand : ICommand
+    {
+        private readonly Action<object?> _execute;
+        private readonly Predicate<object?>? _canExecute;
+
+        public RelayCommand(Action<object?> execute, Predicate<object?>? canExecute = null)
+        {
+            _execute = execute ?? throw new ArgumentNullException(nameof(execute));
+            _canExecute = canExecute;
+        }
+
+        public RelayCommand(Action execute, Func<bool>? canExecute = null)
+            : this(_ => execute(), canExecute == null ? null : _ => canExecute())
+        {
+        }
+
+        public event EventHandler? CanExecuteChanged
+        {
+            add { CommandManager.RequerySuggested += value; }
+            remove { CommandManager.RequerySuggested -= value; }
+        }
+
+        public bool CanExecute(object? parameter)
+        {
+            return _canExecute?.Invoke(parameter) ?? true;
+        }
+
+        public void Execute(object? parameter)
+        {
+            _execute(parameter);
+        }
+
+        public void RaiseCanExecuteChanged()
+        {
+            CommandManager.InvalidateRequerySuggested();
+        }
+    }
+
+    public class AsyncRelayCommand : ICommand
+    {
+        private readonly Func<object?, Task> _execute;
+        private readonly Predicate<object?>? _canExecute;
+        private bool _isExecuting;
+
+        public AsyncRelayCommand(Func<object?, Task> execute, Predicate<object?>? canExecute = null)
+        {
+            _execute = execute ?? throw new ArgumentNullException(nameof(execute));
+            _canExecute = canExecute;
+        }
+
+        public AsyncRelayCommand(Func<Task> execute, Func<bool>? canExecute = null)
+            : this(_ => execute(), canExecute == null ? null : _ => canExecute())
+        {
+        }
+
+        public event EventHandler? CanExecuteChanged
+        {
+            add { CommandManager.RequerySuggested += value; }
+            remove { CommandManager.RequerySuggested -= value; }
+        }
+
+        public bool CanExecute(object? parameter)
+        {
+            return !_isExecuting && (_canExecute?.Invoke(parameter) ?? true);
+        }
+
+        public async void Execute(object? parameter)
+        {
+            if (!CanExecute(parameter))
+                return;
+
+            try
+            {
+                _isExecuting = true;
+                RaiseCanExecuteChanged();
+                await _execute(parameter);
+            }
+            finally
+            {
+                _isExecuting = false;
+                RaiseCanExecuteChanged();
+            }
+        }
+
+        public void RaiseCanExecuteChanged()
+        {
+            CommandManager.InvalidateRequerySuggested();
+        }
+    }
+}