How to Create Rounded Corners WPF Window?

Question

How can i create rounded corners WPF Window using WindowStyle as in the picture below?

@Peter Fleischer (former MVP) Can you help? it's your window!

Answer 1

You could set AllowsTransparency="True" Background="Transparent" WindowStyle="None" and customize events such as maximize, minimize, and close for Window. You can also try to use the WindowChrome class.
MainWindow.xaml.cs:

<Window x:Class="RoundCornerWindow.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:RoundCornerWindow" x:Name="window"  
        mc:Ignorable="d" AllowsTransparency="True" Background="Transparent" WindowStyle="None"  
        Title="MainWindow" Height="450" Width="800">  
    <Border CornerRadius="25" BorderBrush="Black" BorderThickness="2" Padding="6" Background="GhostWhite">  
        <Grid>  
            <Grid VerticalAlignment="Top" Height="30" HorizontalAlignment="Right" Width="230" Margin="0,5,5,0" >  
                <Button Content="*"  Width="25" Margin="200,0,6,0" Click="Close_Click"/>  
                <Button Content="[]"  Width="25"  Margin="170,0,32,0" Click="Maximize_Click"/>  
                <Button Content="-" Width="25"  Margin="125,0,44,0" Click="Minimize_Click"/>  
            </Grid>  
        </Grid>  
    </Border>  
</Window>  

MainWindow.xaml.cs:

 public partial class MainWindow : Window  
  {  
    public MainWindow()  
    {  
      InitializeComponent();  
    }  
    private void Close_Click(object sender, RoutedEventArgs e)  
    {  
     window.Close();  
    }  
    private void Maximize_Click(object sender, RoutedEventArgs e)  
    {  
      if (window.WindowState == WindowState.Normal)  
      {  
        window.WindowState = WindowState.Maximized;  
      }  
      else  
      {  
        window.WindowState = WindowState.Normal;  
      }  
    }  
    private void Minimize_Click(object sender, RoutedEventArgs e)  
    {  
      window.WindowState = WindowState.Minimized;  
    }  
}  

The result:

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Answer 2

With CornerRadius
(I had posted a basic sample in this thread for another problem (shadow))