Resize WPF Window and contents depening on screen resolution

The syntax Height="{Binding SystemParameters.PrimaryScreenHeight}" provides the clue but doesn't work as such. SystemParameters.PrimaryScreenHeight is static, hence you shall use:

  <Window x:Class="MyApp.MainWindow"      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"      xmlns:tools="clr-namespace:MyApp.Tools"      Height="{x:Static SystemParameters.PrimaryScreenHeight}"       Width="{x:Static SystemParameters.PrimaryScreenWidth}"       Title="{Binding Path=DisplayName}"      WindowStartupLocation="CenterScreen"      Icon="icon.ico"  >

And it would fit the whole screen. Yet, you may prefer to fit a percentage of the screen size, e.g. 90%, in which case the syntax must be amended with a converter in a binding spec:

  <Window x:Class="MyApp.MainWindow"      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"      xmlns:tools="clr-namespace:MyApp.Tools"      Height="{Binding Source={x:Static SystemParameters.PrimaryScreenHeight}, Converter={tools:RatioConverter}, ConverterParameter='0.9' }"       Width="{Binding Source={x:Static SystemParameters.PrimaryScreenWidth}, Converter={tools:RatioConverter}, ConverterParameter='0.9' }"       Title="{Binding Path=DisplayName}"      WindowStartupLocation="CenterScreen"      Icon="icon.ico"  >

Where RatioConverter is here declared in MyApp.Tools namespace as follows:

namespace MyApp.Tools {    [ValueConversion(typeof(string), typeof(string))]    public class RatioConverter : MarkupExtension, IValueConverter    {      private static RatioConverter _instance;      public RatioConverter() { }      public object Convert(object value, Type targetType, object parameter, CultureInfo culture)      { // do not let the culture default to local to prevent variable outcome re decimal syntax        double size = System.Convert.ToDouble(value) * System.Convert.ToDouble(parameter,CultureInfo.InvariantCulture);        return size.ToString( "G0", CultureInfo.InvariantCulture );      }      public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)      { // read only converter...        throw new NotImplementedException();      }      public override object ProvideValue(IServiceProvider serviceProvider)      {        return _instance ?? (_instance = new RatioConverter());      }    }}

Where the definition of the converter shall inherit from MarkupExtension in order to be used directly in the root element without a former declaration as a resource.

Just simply make a binding like that:

<Window x:Class="YourApplication.MainWindow"    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    Title="YourApplication"     Height="{Binding SystemParameters.PrimaryScreenHeight}"     Width="{Binding SystemParameters.PrimaryScreenWidth}">

Based on berhauz's answer. But you can simplify it even further by doing it in code behind(.xaml.cs):

public Window1(){    InitializeComponent();    this.Height = SystemParameters.PrimaryScreenHeight * 0.95;    this.Width = SystemParameters.PrimaryScreenWidth * 0.95;}