Check an app's DPI awareness.

App.xaml.cs

public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);

        MessageBox.Show(
            String.Format("IsProcessDPIAware: {0}", IsProcessDPIAware()) + Environment.NewLine +
            String.Format("GetDpiAwareness: {0}", GetDpiAwareness()));
    }

    [DllImport("User32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool IsProcessDPIAware();

    [DllImport("Shcore.dll", SetLastError = true)]
    public static extern int GetProcessDpiAwareness(
        IntPtr hprocess,
        out PROCESS_DPI_AWARENESS value);

    public enum PROCESS_DPI_AWARENESS
    {
        /// <summary>
        /// Not DPI aware
        /// </summary>
        Process_DPI_Unaware = 0,

        /// <summary>
        /// System DPI aware
        /// </summary>
        Process_System_DPI_Aware = 1,

        /// <summary>
        /// Per-Monitor DPI aware
        /// </summary>
        Process_Per_Monitor_DPI_Aware = 2
    }        

    public static PROCESS_DPI_AWARENESS? GetDpiAwareness()
    {
        PROCESS_DPI_AWARENESS value;
        var result = GetProcessDpiAwareness(
            IntPtr.Zero, // Current process
            out value);
        if (result != 0) // 0 means S_OK.
            return null;

        return value;
    }
}