C# wpf解决Popup弹出位置异常问题解决

<Window x:Class="WPFApp1.MainWindow"
        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"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="360" Width="640">
    <Grid>
        <ToggleButton x:Name="Btn_Popup"  Width="70" Height="35"  Content="弹出"  />
        <Popup  x:Name="Popup1" 
                            Placement="Relative"
                            AllowsTransparency="True"
                            PlacementTarget="{Binding ElementName=Btn_Popup}" 
                            IsOpen="{Binding IsChecked, ElementName=Btn_Popup}"
                            StaysOpen="False"
                            Width="120" 
                            Height="120"
                            HorizontalOffset="80" 
                            VerticalOffset="-125"                        
                            >
            <Grid>
                <Border   Width="120" Height="60" BorderBrush="#333333" BorderThickness="1" CornerRadius="10" Background="White" >
                    <TextBlock Text="弹出框"  FontSize="16" HorizontalAlignment="Center" VerticalAlignment="Center" />
                </Border>
            </Grid>
        </Popup>
    </Grid>
</Window>

        [DllImport("user32.dll", EntryPoint = "SystemParametersInfo", SetLastError = true)]
        public static extern bool SystemParametersInfoSet(uint action, uint uiParam, uint vparam, uint init);
        void SetMenuAlign()
         {
         //uiParam为false时设置弹出菜单左对齐，true则右对齐
         SystemParametersInfoSet(0x001C , 0, 0, 0);
         }

<Window x:Class="WpfApp1.MainWindow"
        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"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="360" Width="640">
    <Grid>
        <ToggleButton x:Name="Btn_Popup"  Width="70" Height="35"  Content="点击弹出"  />
        <Popup  x:Name="Popup1" 
                            Placement="Absolute"
                            AllowsTransparency="True"
                            PlacementTarget="{Binding ElementName=Btn_Popup}" 
                            IsOpen="{Binding IsChecked, ElementName=Btn_Popup}"
                            StaysOpen="False"
                            Width="120" 
                            Height="120"
                            HorizontalOffset="80" 
                            VerticalOffset="-100"    
                            Opened="Popup1_Opened"      
                            >
            <Grid>
                <Border   Width="120" Height="60" BorderBrush="#333333" BorderThickness="1" CornerRadius="10" Background="White" >
                    <TextBlock Text="弹出框"  FontSize="16" HorizontalAlignment="Center" VerticalAlignment="Center" />
                </Border>
            </Grid>
        </Popup>
    </Grid>
</Window>

 private void Popup1_Opened(object sender, EventArgs e)
        {
            Popup pop = sender as Popup;
            if (pop == null)
                return;
            if (pop.PlacementTarget == null)
                return;
            if (pop.Placement == PlacementMode.Absolute)
            {
                var relative = pop.PlacementTarget.PointToScreen(new Point(0, 0));
                pop.HorizontalOffset = relative.X + 80;
                pop.VerticalOffset = relative.Y + -100;
            }
        }