WPF center screen issues

Question

I have my WPF xaml as follows

<Window
        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"
        xmlns:Usercontrols="clr-namespace:WPFApp1.Usercontrols" x:Class="WPFApp1.Window1"
        mc:Ignorable="d"
        Title="Window1" Width="763" Height="950" ResizeMode="NoResize" Loaded="Window_Loaded">
    <Grid Height="224" Width="Auto">

        <CheckBox x:Name="Checkbox1" Width="100px" Height="25px" Content="Checkbox" Margin="90,-120,567,319"/>
        <CheckBox x:Name="Checkbox2" Height="25px" Content="Checkbox1"  Margin="178,-120,457,319"/>
        <CheckBox x:Name="Checkbox3" Width="Auto" Content="Checkbox2"  Margin="296,-120,309,319"/>
        <CheckBox x:Name="Checkbox4" Width="Auto" Content="Checkbox3"  Margin="420,-120,213,319"/>

        <GroupBox Name="grp1" Header="Group1" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="92,56,0,98" Width="590" Height="70" IsEnabled="False">

        </GroupBox>
        <GroupBox Name="grp2" Header="Group2" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="92,136,0,18" Width="590" Height="70" IsEnabled="False">

        </GroupBox>

    </Grid>
</Window>

 I have written as follows to center the screen

double width = window.ActualWidth;
            double height = window.ActualHeight;

            if (m_firstTime) // First time ActualWidth and ActualHeight is not set
            {
                if (!Double.IsNaN(window.Width)) { width = window.Width; }
                if (!Double.IsNaN(window.Height)) { height = window.Height; }

                m_firstTime = false;
            }

            // Set Left and Top manually and calculate center of screen.
            window.Left = (SystemParameters.WorkArea.Width - width) / 2
                + SystemParameters.WorkArea.Left;
            window.Top = (SystemParameters.WorkArea.Height - height) / 2
                + SystemParameters.WorkArea.Top;

 But in my laptop it is going to the top so that few controls not getting visible so can some one help me to center on any screen resolution