c# - 动态创建 xaml 对象时收到未声明的前缀

Question

见鬼，我目前正在尝试在代码中动态创建一些对象。这已经成功到我想要识别元素的地步在这里，我创建了对象(带阴影的椭圆)

public MainPage()
    {
        InitializeComponent();
        Loaded += new RoutedEventHandler(MainPage_Loaded);
    }

    void MainPage_Loaded(object sender, RoutedEventArgs e)
    {
        var element = CreateEllipse();
        LayoutRoot.Children.Add(element);
    }

    public Ellipse CreateEllipse()
    {
        StringBuilder xaml = new StringBuilder();
        string ns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation";
        xaml.Append("<Ellipse ");
        xaml.Append(string.Format("xmlns='{0}'", ns));
        xaml.Append(" x:Name='myellipse'"); //causes the exception
        xaml.Append(" Margin='50 10 50 10'");
        xaml.Append(" Grid.Row='0'");
        xaml.Append(" Fill='#FD2424FF'");
        xaml.Append(" Stroke='Black' >");
        xaml.Append("<Ellipse.Effect>");
        xaml.Append("<DropShadowEffect/>");
        xaml.Append(" </Ellipse.Effect>");
        xaml.Append(" </Ellipse>");
        var ellipse = (Ellipse)XamlReader.Load(xaml.ToString());
        return ellipse;
    }

我想做的是在创建对象后，我希望能够使用 VisualTreeHelper 定位父对象。

public void button1_Click(object sender, RoutedEventArgs e)
    {
        DependencyObject o = myellipse;
        while ((o = VisualTreeHelper.GetParent(o)) != null)
        {
            textBox1.Text = (o.GetType().ToString());
        }
    }

任何人都可以指出在这样的场景中引用动态创建的对象的正确方向，或者如何以编程方式正确定义对象的 x:Name 吗？

谢谢，

Answer 1

Can anyone point me in the right direction for referencing a dynamically created object in a scenario like this or how to properly define x:Name for an object programatically?

您不能像这样使用动态生成的类型直接引用“myellipse”。编译器将x:Name 转换为类型在编译时 - 因为您是在运行时加载它，所以它不会存在。

相反，您可以制作一个“myellipse”变量，并让您的动态生成例程设置它:

void MainPage_Loaded(object sender, RoutedEventArgs e)
{
    var element = CreateEllipse();
    LayoutRoot.Children.Add(element);
}

private Ellipse myEllipse; 
public Ellipse CreateEllipse()
{
    StringBuilder xaml = new StringBuilder();
    string ns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation";
    xaml.Append("<Ellipse ");
    xaml.Append(string.Format("xmlns='{0}'", ns));
    xaml.Append(" Margin='50 10 50 10'");
    xaml.Append(" Grid.Row='0'");
    xaml.Append(" Fill='#FD2424FF'");
    xaml.Append(" Stroke='Black' >");
    xaml.Append("<Ellipse.Effect>");
    xaml.Append("<DropShadowEffect/>");
    xaml.Append(" </Ellipse.Effect>");
    xaml.Append(" </Ellipse>");
    this.myEllipse = (Ellipse)XamlReader.Load(xaml.ToString());

    return this.myEllipse;
}

也就是说，我建议不要使用这样的字符串来构建椭圆。您可以直接创建椭圆类，然后添加效果。在这种情况下，您不需要使用 XamlReader 来解析字符串。

private Ellipse myEllipse; 
public Ellipse CreateEllipse()
{
     this.myEllipse = new Ellipse();
     this.myEllipse.Effect = new DropShadowEffect();
     Grid.SetRow(this.myEllipse, 0);
     // Set properties as needed

     return this.myEllipse;
}