Using GetNativeSystemInfo from UWP app

gistfile1.txt

[DllImport("api-ms-win-core-sysinfo-l1-2-3.dll")]
static extern void GetNativeSystemInfo(ref SYSTEM_INFO lpSystemInfo);

[StructLayout(LayoutKind.Sequential)]
public struct SYSTEM_INFO
{
  public ushort processorArchitecture;
  ushort reserved;
  public uint pageSize;
  public IntPtr minimumApplicationAddress;
  public IntPtr maximumApplicationAddress;
  public IntPtr activeProcessorMask;
  public uint numberOfProcessors;
  public uint processorType;
  public uint allocationGranularity;
  public ushort processorLevel;
  public ushort processorRevision;
}

...

  var si = new SYSTEM_INFO();
  GetNativeSystemInfo(ref si);

  Windows.System.ProcessorArchitecture at = (Windows.System.ProcessorArchitecture)si.processorArchitecture;
  string architecture = at.ToString();

  if( 12 == (int)at)
  {
      architecture = "Arm64";
  }