非根对象中的 XAML 事件处理程序答案

【问题标题】：XAML event handler in a nonroot object非根对象中的 XAML 事件处理程序
【发布时间】：2019-03-11 17:46:40
【问题描述】：

想象一下以下 XAML：

<Page
    x:Class="MyProject.MainPage"
    xmlns:local="using:MyProject">

   <local:MyStackPanel>
       <Button Content="Go" Click="OnGo"/>
   </local:MyStackPanel>
</Page>

XAML 假定 OnGo 是页面类中的一个方法。我可以以某种方式以声明方式告诉它OnGo 位于MyStackPanel 中吗？

我知道我可以在页面加载后以编程方式分配事件处理程序。我想知道是否可以通过纯粹的 XAML 方式实现。 “不”是一个可以接受的答案:)

【问题讨论】：

标签： xaml uwp-xaml

【解决方案1】：

根据您的要求，您可以将 MyStackPanel DataContext 与自身绑定。然后在MyStackPanel类中创建用于绑定按钮命令的BtnClickCommand，如下所示。

public class MyStackPanel : StackPanel
{
    public MyStackPanel()
    {

    }

    public ICommand BtnClickCommand
    {
        get
        {
            return new RelayCommand(() =>
            {


            });
        }
    }

}
public class RelayCommand : ICommand
{
    private readonly Action _execute;
    private readonly Func<bool> _canExecute;
    /// <summary>
    /// Raised when RaiseCanExecuteChanged is called.
    /// </summary>
    public event EventHandler CanExecuteChanged;
    /// <summary>
    /// Creates a new command that can always execute.
    /// </summary>
    /// <param name="execute">The execution logic.</param>
    public RelayCommand(Action 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 execute, Func<bool> canExecute)
    {
        if (execute == null)
            throw new ArgumentNullException("execute");
        _execute = execute;
        _canExecute = canExecute;
    }
    /// <summary>
    /// Determines whether this RelayCommand can execute in its current state.
    /// </summary>
    /// <param name="parameter">
    /// Data used by the command. If the command does not require data to be passed,
    /// this object can be set to null.
    /// </param>
    /// <returns>true if this command can be executed; otherwise, false.</returns>
    public bool CanExecute(object parameter)
    {
        return _canExecute == null ? true : _canExecute();
    }
    /// <summary>
    /// Executes the RelayCommand on the current command target.
    /// </summary>
    /// <param name="parameter">
    /// Data used by the command. If the command does not require data to be passed,
    /// this object can be set to null.
    /// </param>
    public void Execute(object parameter)
    {
        _execute();
    }
    /// <summary>
    /// Method used to raise the CanExecuteChanged event
    /// to indicate that the return value of the CanExecute
    /// method has changed.
    /// </summary>
    public void RaiseCanExecuteChanged()
    {
        var handler = CanExecuteChanged;
        if (handler != null)
        {
            handler(this, EventArgs.Empty);
        }
    }
}

用法

<local:MyStackPanel DataContext="{Binding RelativeSource={RelativeSource Mode=Self}}">
    <Button Command="{Binding BtnClickCommand}" Content="ClickMe" />
</local:MyStackPanel>

【讨论】：

谢谢。不过，几乎没有声明性。
@SevaAlekseyev 这个答案不符合要求吗？
没有任何要求，只是希望 XAML 比我知道的更灵活 :) 显然不是。
@SevaAlekseyev，好吧，Xaml 不灵活。它不能做你想做的事。欢迎您在UserVoice发帖。