c# - 按钮命令绑定不起作用

Question

我创建了一个新的 UserContol，里面有一个按钮。我想像这样将按钮命令绑定到新用户控件的依赖属性。

<Grid>
 <Button Name="Button1" Command="{Binding Button1Command}" />
</Grid>

这是包含 UserControl 上的 DP：

public ICommand Button1Command
{
  get { return (ICommand)GetValue(Button1CommandProperty); }
  set { SetValue(Button1CommandProperty, value); }
}

public static readonly DependencyProperty Button1CommandProperty =
    DependencyProperty.Register("Button1Command", typeof(ICommand), typeof(BptCellTemplate), new FrameworkPropertyMetadata(null));

当我尝试使用它时，当我按下按钮时没有任何反应。它不识别命令。如果我添加一个事件，它会起作用。像这样：

 public static readonly DependencyProperty Button1CommandProperty =
    DependencyProperty.Register("Button1Command", typeof(ICommand), typeof(BptCellTemplate), new FrameworkPropertyMetadata(null, OnButton1CommandChanged));

private static void OnButton1CommandChanged(DependencyObject dependencyObject,
                                              DependencyPropertyChangedEventArgs args)
{
  var bptCellTemplate = dependencyObject as BptCellTemplate;
  if (bptCellTemplate == null || !(args.NewValue is ICommand))
  {
    return;
  }
  (bptCellTemplate.DataContext as BptCellTemplateViewModel).Button1Command = (ICommand)args.NewValue;

}

有没有办法在没有事件的情况下绑定它？因为它适用于我以相同方式执行的其他按钮属性（Visibility例如）

score 3 · Accepted Answer

您的绑定可能不起作用，因为没有任何内容表明该Button1Command属性是您的UserControl.

在 Visual Studio 中调试程序时，您可以通过查看“输出”窗口来确认这是问题所在。您可能会看到Button1Command找不到成员的绑定错误。

解决此问题的典型方法是向您UserControl的根元素添加一个名称属性，例如x:Name="root"（您可以选择自己的名称或使用现有名称（如果有））。然后，将您的绑定更改为引用新名称的命令：

<Button Name="Button1" Command="{Binding Button1Command, ElementName=root}" />

score 1 · Accepted Answer

您需要类实现 ICommand 接口。

public class RelayCommand : ICommand
{
    #region Fields

    readonly Action<object> _execute;
    readonly Predicate<object> _canExecute;

    #endregion // Fields

    #region Constructors

    /// <summary>
    /// Creates a new command that can always execute.
    /// </summary>
    /// <param name="execute">The execution logic.</param>
    public RelayCommand(Action<object> execute)
        : this(execute, null)
    {
    }

    /// <summary>
    /// Creates a new command.
    /// </summary>
    /// <param name="execute">The execution logic.</param>
    /// <param name="canExecute">The execution status logic.</param>
    public RelayCommand(Action<object> execute, Predicate<object> canExecute)
    {
        if (execute == null)
            throw new ArgumentNullException("execute");

        _execute = execute;
        _canExecute = canExecute;
    }

    #endregion // Constructors

    #region ICommand Members

    [DebuggerStepThrough]
    public bool CanExecute(object parameter)
    {
        return _canExecute == null ? true : _canExecute(parameter);
    }

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

    public void Execute(object parameter)
    {
        _execute(parameter);
    }

    #endregion // ICommand Members
}

现在绑定很简单。在您的 DataContext 中定义命令（MVVM ...等）不要记住设置 DataContext ...例如 DataContext = this; （这是你的窗口）

RelayCommand _btnCommand;
public ICommand Button1Command
{
    get
    {
        if (_btnCommand == null)
        {
            _btnCommand = new RelayCommand(param => this.ExecuteButton1(),
                param => this.CanButton1());
        }
        return _btnCommand;
    }
}

public void ExecuteButton1()
{
}

public bool CanButton1()
{
    return true;
}

而已 ...

c# - 按钮命令绑定不起作用

2 回答 2

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