How to create custom window chrome in wpf?

You set your Window's WindowStyle="None", then build your own window interface. You need to build in your own Min/Max/Close/Drag event handlers, but Resizing is still maintained.

For example:

<Window 
    WindowState="Maximized"
    WindowStyle="None"
    WindowStartupLocation="CenterScreen"
    MaxWidth="{Binding Source={x:Static SystemParameters.WorkArea}, Path=Width}"
    MaxHeight="{Binding Source={x:Static SystemParameters.WorkArea}, Path=Height}"
>

    <DockPanel x:Name="RootWindow">
        <DockPanel x:Name="TitleBar" DockPanel.Dock="Top">
            <Button x:Name="CloseButton" Content="X"
                    Click="CloseButton_Click"
                    DockPanel.Dock="Right" />
            <Button x:Name="MaxButton" Content="Restore"
                    Click="MaximizeButton_Click"
                    DockPanel.Dock="Right" />
            <Button x:Name="MinButton" Content="Min"
                    Click="MinimizeButton_Click"
                    DockPanel.Dock="Right" />

            <TextBlock HorizontalAlignment="Center">Application Name</TextBlock>
        </DockPanel>

        <ContentControl Content="{Binding CurrentPage}" />
    </DockPanel>

</Window>

And here's some example code-behind for common window functionality

/// <summary>
/// TitleBar_MouseDown - Drag if single-click, resize if double-click
/// </summary>
private void TitleBar_MouseDown(object sender, MouseButtonEventArgs e)
{
    if(e.ChangedButton == MouseButton.Left)
        if (e.ClickCount == 2)
        {
            AdjustWindowSize();
        }
        else
        {
            Application.Current.MainWindow.DragMove();
        }
 }

/// <summary>
/// CloseButton_Clicked
/// </summary>
private void CloseButton_Click(object sender, RoutedEventArgs e)
{
   Application.Current.Shutdown();
}

/// <summary>
/// MaximizedButton_Clicked
/// </summary>
private void MaximizeButton_Click(object sender, RoutedEventArgs e)
{
    AdjustWindowSize();
}

/// <summary>
/// Minimized Button_Clicked
/// </summary>
private void MinimizeButton_Click(object sender, RoutedEventArgs e)
{
    this.WindowState = WindowState.Minimized;
}

/// <summary>
/// Adjusts the WindowSize to correct parameters when Maximize button is clicked
/// </summary>
private void AdjustWindowSize()
{
    if (this.WindowState == WindowState.Maximized)
    {
        this.WindowState = WindowState.Normal;
        MaxButton.Content = "1";
    }
    else
    {
        this.WindowState = WindowState.Maximized;
        MaxButton.Content = "2";
    }

}

.NET 4.5 added a new class that greatly simplifies this.

The WindowChrome class enables you to extend Windows Presentation Foundation (WPF) content into the non-client area of a window that is typically reserved for the operating system’s window manager.

You can find a tutorial here.

And here's a short example usage.