c# - 在自定义用户控件中公开事件 - Window Store App

Question

我似乎在 Xaml 中公开事件时遇到问题。我已经在这样的自定义用户控件中声明了一个公共(public)事件处理程序。

public sealed partial class FoodItemControl : UserControl
{
    public event EventHandler<StringEventArgs> thumbnailClicked;

    public FoodItemControl()
    {
        InitializeComponent();
        (this.Content as FrameworkElement).DataContext = this;
    }



    private void Thumbnail_Tapped(object sender, TappedRoutedEventArgs e)
    {
        var handler = thumbnailClicked;
        if (handler != null)
        {
            handler(this, new StringEventArgs());
        }
    }
}

但是当我在 xaml 中为其分配事件时，找不到公开的事件处理程序。即

<local:FoodItemControl thumbnailClicked="SOMETHING" />

我是否遗漏了我找到的示例中的某些内容？

编辑:看来我的问题是我将事件定义为 EventHandler< StringEventArgs >。一旦我将其更改为简单的 EventHandler I.e，它就起作用了

public event EventHandler thumbnailedClicked;

但是我还是不太明白这是为什么？

Answer 1

您必须创建一个依赖属性并注册该属性以在用户控件中公开它:

public sealed partial class FoodItemControl : UserControl
{
    public EventHandler thumbnailClicked
    {
        get { return (EventHandler)GetValue(thumbnailClickedProperty); }
        set { SetValue(thumbnailClickedProperty, value); }
    }

    public static readonly DependencyProperty thumbnailClickedProperty =
  DependencyProperty.Register("thumbnailClicked", typeof(EventHandler),
    typeof(FoodItemControl), new PropertyMetadata(""));


    public FoodItemControl()
    {
        this.InitializeComponent();
        (this.Content as FrameworkElement).DataContext = this;
    }
}