我正在尝试使用MVVM模式制作一个简单的WPF应用程序。我写了一个实现ICommand接口的类：

public class RelayCommand : ICommand
    {
        private action<object> execute;
        private Func<object,bool> canExecute;

        public event EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }

        public RelayCommand(action<object> execute,Func<object,bool> canExecute = null)
        {
            this.execute = execute;
            this.canExecute = canExecute;
        }

        public bool CanExecute(object parameter)
        {
            return this.canExecute == null || this.canExecute(parameter);
        }

        public void Execute(object parameter)
        {
            this.execute(parameter);
        }
    }

然后，当我单击视图中的按钮时，通过将页面分配给当前页面来使用它来显示新页面

public ICommand bFirst_Click
    {
        get
        {
            return new RelayCommand(o => CurrentPage = first);
        }
    }

视图中的XAML代码

    <StackPanel>
        <Button Command="{Binding bFirst_Click}" Content="First"/>
    </StackPanel>
    <Frame
        Grid.Column="1"
        Content="{Binding CurrentPage}"
        NavigationUIVisibility="Hidden"
        Opacity="{Binding FrameOpacity}"
        />

但是什么也没发生。请帮助我，我错过了什么，还是做错了吗？