WPF实现窗体中的悬浮按钮

WPF实现窗体中的悬浮按钮，按钮可拖动，吸附停靠在窗体边缘。

控件XAML代码：

<Button x:Class="SunCreate.Common.Controls.FloatButton"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300"
             Width="50" Height="50" Margin="0" 
             HorizontalAlignment="Left" VerticalAlignment="Top" 
             x:Name="btn"
             Loaded="btn_Loaded" Click="btn_Click" >
    <Button.Template>
        <ControlTemplate>
            <Grid MouseLeftButtonDown="Border_MouseLeftButtonDown">
                <Border CornerRadius="25" Background="#022938" Opacity="0.2" >
                </Border>
                <Border CornerRadius="20" Width="40" Height="40" Background="#022938" Opacity="0.3" >
                </Border>
                <Border CornerRadius="14" Width="28" Height="28" Background="#b06919" Opacity="0.8" >
                </Border>
            </Grid>
        </ControlTemplate>
    </Button.Template>
</Button>

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