值不能为null CommandBinding自定义命令

Question

我刚刚开始使用WPF,并且遇到了一个我不明白的问题.

我收到以下错误:

值不能为空.Parametername:值

这里发生错误:

<Window.CommandBindings>
        <CommandBinding Command="self:CustomCommands.Exit" Executed="ExitCommand_Executed" CanExecute="ExitCommand_CanExecute"/>
</Window.CommandBindings>

我当然xmlns:self="clr-namespace:PrintMonitor"在xaml中设置了命名空间.

代码隐藏:

namespace PrintMonitor
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void ExitCommand_CanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            if(e != null)
                e.CanExecute = true;
        }

        private void ExitCommand_Executed(object sender, ExecutedRoutedEventArgs e)
        {
            Application.Current.Shutdown();
        }
    }

    public static class CustomCommands
    {
        public static readonly RoutedUICommand Exit = new RoutedUICommand
                (
                        "Beenden",
                        "Exit",
                        typeof(CustomCommands),
                        new InputGestureCollection()
                        {
                            new KeyGesture(Key.F4, ModifierKeys.Alt)
                        }
                );
    }
}

那么,如果我使用自定义命令,为什么会出现此错误,但如果我使用自动命令,则会出现此问题Command="ApplicationCommands.New",如何修复此错误？

该代码是本教程的一部分.

Answer 1

单击设计器窗口下方的“启用项目代码”按钮

Answer 2

也许您需要将 CustomCommands 设置为非静态，

并让 MainWindow 的 DataContext 为 CustomCommands

 public class CustomCommands
 {
        public static readonly RoutedUICommand Exit = new RoutedUICommand
                (
                        "Beenden",
                        "Exit",
                        typeof(CustomCommands),
                        new InputGestureCollection()
                        {
                            new KeyGesture(Key.F4, ModifierKeys.Alt)
                        }
                );
 }

public partial class MainWindow : Window
{
    public  CustomCommands CM;
    public MainWindow()
    {
        CM = new  CustomCommands();
        this.DataContext = CM;
        InitializeComponent();

    }

    private void ExitCommand_CanExecute(object sender, CanExecuteRoutedEventArgs e)
    {
        if(e != null)
            e.CanExecute = true;
    }

    private void ExitCommand_Executed(object sender, ExecutedRoutedEventArgs e)
    {
        Application.Current.Shutdown();
    }

}