LinearGradientBrush指的是一个线性的坡度类，用它和GradientStop类可以为一个圆形区域填充渐变的颜色。
例如：
代码
<UserControl x:Class="win7.clock"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400">
<Grid x:Name="LayoutRoot" Background="White">
<Ellipse Height="200" Width="200">
<Ellipse.Fill>
<LinearGradientBrush StartPoint="0,0" EndPoint="1,1">
<GradientStop Color="Red" Offset="0.2"></GradientStop>
<GradientStop Color="Green" Offset="0.3"></GradientStop>
<GradientStop Color="Blue" Offset="0.5"></GradientStop>
<GradientStop Color="Yellow" Offset="0.9"></GradientStop>
</LinearGradientBrush>
</Ellipse.Fill>
</Ellipse>
</Grid>
</UserControl>
效果如下：
代码
<UserControl x:Class="win7.clock"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400">
<Grid x:Name="LayoutRoot" Background="White">
<Ellipse Height="200" Width="200">
<Ellipse.Fill>
<LinearGradientBrush StartPoint="0.5,0" EndPoint="0.5,1">
<GradientStop Color="Red" Offset="0.2"></GradientStop>
<GradientStop Color="Green" Offset="0.3"></GradientStop>
<GradientStop Color="Blue" Offset="0.5"></GradientStop>
<GradientStop Color="Yellow" Offset="0.9"></GradientStop>
</LinearGradientBrush>
</Ellipse.Fill>
</Ellipse>
</Grid>
</UserControl>
效果如下：
