在 WPF 中, 按钮包含一个 “边框”, 很多时候需要设置按钮的圆角, 但是按钮并没有提供一个属性用来设置边框圆角.

下面以按钮为例, 列举几种常用的设置圆角的方式.

通过附加属性

定义一个附加属性, 然后在各个地方就能直接方便的使用了, 下面是实际使用方式:

<Button utils.BorderUtils.CornerRadius="3"/>

接下来是具体实现代码, 首先是一些工具方法:

using System.Windows.Media;namespace System.Windows
{public static class CommonUtils{public static void RunOnFirstLoaded(this FrameworkElement element, EventHandler handler){void Once(object? sender, RoutedEventArgs e){element.Loaded -= Once;handler.Invoke(sender, e);}if (element.IsLoaded)handler.Invoke(element, EventArgs.Empty);elseelement.Loaded += Once;}public static TElement? GetElementFromVisualTree<TElement>(this FrameworkElement control) where TElement : FrameworkElement{if (control is TElement ele)return ele;int childrenCount = VisualTreeHelper.GetChildrenCount(control);for (int i = 0; i < childrenCount; i++){DependencyObject child = VisualTreeHelper.GetChild(control, i);if (child is TElement eleChild)return eleChild;}return null;}}
}

然后是 BorderUtils 这个类, 在其中定义 CornerRadius 附加属性:

using System;
using System.Windows.Controls;
using System.Windows.Media;namespace System.Windows
{public static class BorderUtils{[AttachedPropertyBrowsableForType(typeof(FrameworkElement))]public static CornerRadius GetCornerRadius(DependencyObject obj){return (CornerRadius)obj.GetValue(CornerRadiusProperty);}public static void SetCornerRadius(DependencyObject obj, CornerRadius value){obj.SetValue(CornerRadiusProperty, value);}// Using a DependencyProperty as the backing store for CornerRadius.  This enables animation, styling, binding, etc...public static readonly DependencyProperty CornerRadiusProperty =DependencyProperty.RegisterAttached("CornerRadius", typeof(CornerRadius), typeof(BorderUtils), new PropertyMetadata(new CornerRadius(), CornerRadiusChanged));private static void CornerRadiusChanged(DependencyObject d, DependencyPropertyChangedEventArgs e){if (d is not FrameworkElement ele)return;ele.RunOnFirstLoaded((s, _e) =>{if (CommonUtils.GetElementFromVisualTree<Border>(ele) is not Border border)return;border.CornerRadius = (CornerRadius)e.NewValue;});}}
}

通过资源

直接在 Button 节点下添加一个 Border 的样式资源, 然后 Button 中的 Border 就会应用这个样式.

<Button><Button.Resources><Style TargetType="Border"><Setter Property="CornerRadius" Value="3" /></Style></Button.Resources>
</Button>

通过模板

很麻烦的一种方式, 不推荐

<Button><Button.Template><ControlTemplate TargetType="{x:Type Button}" ><Border BorderBrush="{TemplateBinding Control.BorderBrush}" BorderThickness="1" CornerRadius="7,7,7,7"><Border.Background>#FFDDDDDD</Border.Background><ContentPresenter Content="{TemplateBinding ContentControl.Content}" HorizontalAlignment="Center" VerticalAlignment="Center" ></ContentPresenter></Border></ControlTemplate></Button.Template>
</Button>