How can I make the grid back ground to be stretch that it can fit to all resolutions ??

<StackPanel><!-- It's important that this is in the end of the XAML as it needs to be on top of everything else! --><Grid x:Name="InputBox" Visibility="Collapsed"><Grid Background="Black" Opacity="0.5" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" /><Border
            MinWidth="500"
            Background="HotPink" 
            BorderBrush="Black" 
            BorderThickness="1" 
            HorizontalAlignment="Center" 
            VerticalAlignment="Center"><StackPanel><TextBlock Margin="5" Text="Information:" FontWeight="Bold" FontFamily="Cambria" /><TextBlock Foreground="Black" >
                          User have to stand in a position where the kinect is able to detect the whole body of the user.<LineBreak/>
                           Once the Kinecy detects the skeleton user is able to seat in the position for posture correction analysis to take place..<LineBreak/>
                            There will be 3 posture : Hunching , Good , Slouching.
                            It will also detects whether the user is working or resting.
                            Data will be extracted out once skeleton is tracked.</TextBlock><StackPanel Orientation="Horizontal" HorizontalAlignment="Center"><Button x:Name="OkButton" Margin="5" Content="Ok" Background="{x:Null}" Click="btnClose_Click"/></StackPanel></StackPanel></Border></Grid></StackPanel>