WPF 如何通过代码创建一个包含 Canvas 作为内容的 DataTemplate？

Question

我有 XAML 定义的数据模板如下：

<DataTemplate x:Key="PointPushPinItemTemplate">
    <mapControl:MapItem mapControl:MapPanel.Location="{Binding}" >
        <Canvas>
            <Path StrokeThickness="2" Fill="Aqua">
                <Path.Data>
                    <EllipseGeometry RadiusX="10" RadiusY="10"/>
                </Path.Data>
            </Path>
        </Canvas>
    </mapControl:MapItem>
</DataTemplate>

我使用下面的代码创建它，但失败了：

private DataTemplate PushPinPointDataTemplate()
{
    var pointItemFactory = new FrameworkElementFactory(typeof(MapItem));
    pointItemFactory.SetValue(MapPanel.LocationProperty, new Binding());
    var pointCanvas = new Canvas();
    pointCanvas.Children.Add(new Path
    {
        StrokeThickness = 2.0,
        Fill = new SolidColorBrush(Colors.Yellow),
        Data = new EllipseGeometry {RadiusX = 3, RadiusY = 3}
    });

    //below line always throw exception that FrameworkElementFactory.SetValue can't set a visual value
    pointItemFactory.SetValue(MapItem.ContentProperty, pointCanvas);
    return new DataTemplate
    {
        DataType = typeof(Location),
        VisualTree = pointItemFactory
    };
}

如何实现？以前，我在没有 Canvas 的情况下实现了这一点，但对于这种情况，Canvas 是内容控件的内容。 ps: mapControl:MapItem 是继承自 ListBoxItem 的 UI 元素 mapControl:MapPanel.位置是附件属性

Answer 1

您还需要为 Canvas 和 Path 创建工厂：

private DataTemplate PushPinPointDataTemplate()
{
    var pointItemFactory = new FrameworkElementFactory(typeof(MapItem));
    pointItemFactory.SetValue(MapPanel.LocationProperty, new Binding("."));

    var pathFactory = new FrameworkElementFactory(typeof(Path));
    pathFactory.SetValue(Path.StrokeThicknessProperty, 2.0);
    pathFactory.SetValue(Path.FillProperty, Brushes.Yellow);
    pathFactory.SetValue(Path.DataProperty, new EllipseGeometry { RadiusX = 3, RadiusY = 3 });

    var pointCanvasFactory = new FrameworkElementFactory(typeof(Canvas));
    pointCanvasFactory.AppendChild(pathFactory);

    pointItemFactory.AppendChild(pointCanvasFactory);
    return new DataTemplate
    {
        DataType = typeof(Location),
        VisualTree = pointItemFactory
    };
}

请注意，使用 FrameworkElementFactory 以编程方式创建模板是一种已弃用的方法：https://msdn.microsoft.com/en-us/library/system.windows.frameworkelementfactory(v=vs.110).aspx。

The recommended way to programmatically create a template is to load XAML from a string or a memory stream using the Load method of the XamlReader class.

WPF 如何通过代码创建一个包含 Canvas 作为内容的 DataTemplate？

WPF How to Create a DataTemplate Which has Canvas As Content By Code?

c#

wpf

xaml

datatemplate