测试如下事件和方法：
UIElement：
OnRender方法。
LayoutUpdated事件。
FrameworkElement：
OnMeasureOverride方法。
OnArrangeOverride方法。
Loaded事件。
Initialized事件。
以及自定义控件中的依赖属性设置。
class TestControl: Control
{
public TestControl()
{
Loaded += new RoutedEventHandler(TestControl_Loaded);
Initialized += new EventHandler(TestControl_Initialized);
LayoutUpdated += new EventHandler(TestControl_LayoutUpdated);
}
#region Prop
public static readonly DependencyProperty PropProperty =
DependencyProperty.Register("Prop", typeof(bool), typeof(TestControl),
new FrameworkPropertyMetadata((bool)false,
FrameworkPropertyMetadataOptions.AffectsRender,
new PropertyChangedCallback(OnPropChanged),
new CoerceValueCallback(CoerceProp)));
public bool Prop
{
get { return (bool)GetValue(PropProperty); }
set { SetValue(PropProperty, value); }
}
private static void OnPropChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
Debug.WriteLine("DP:Changed");
}
private static object CoerceProp(DependencyObject d, object value)
{
Debug.WriteLine("DP:Coerce");
return value;
}
#endregion
void TestControl_LayoutUpdated(object sender, EventArgs e)
{
Debug.WriteLine("UIElement.LayoutUpdated");
}
void TestControl_Initialized(object sender, EventArgs e)
{
Debug.WriteLine("FrameworkElement.Initialized");
}
void TestControl_Loaded(object sender, RoutedEventArgs e)
{
Debug.WriteLine("FrameworkElement.Loaded");
}
protected override Size MeasureOverride(Size constraint)
{
Debug.WriteLine("FrameworkElement.MeasureOverride");
return base.MeasureOverride(constraint);
}
protected override Size ArrangeOverride(Size arrangeBounds)
{
Debug.WriteLine("FrameworkElement.ArrangeOverride");
return base.ArrangeOverride(arrangeBounds);
}
protected override void OnRender(DrawingContext drawingContext)
{
Debug.WriteLine("UIElement.OnRender");
base.OnRender(drawingContext);
}
}然后在XAML中创建控件并设置依赖属性：
<loc:TestControl Prop="True"/>结果：
DP:Coerce
DP:Changed
FrameworkElement.Initialized
FrameworkElement.MeasureOverride
FrameworkElement.ArrangeOverride
UIElement.OnRender
UIElement.LayoutUpdated
UIElement.LayoutUpdated
FrameworkElement.Loaded 所以，当所有属性初始化后，FrameworkElement.Initialized会运行，接着发生控件就要开始显示了，所以WPF的Measure和Arrange的两步布局步骤就开始了，最后OnRender被调用，控件就显示了。然后UIElement.LayoutUpdated控件此时已经显示，最后Loaded事件发生代表所有预处理项已完成。