How to get parent process in .NET in managed way

Here is a solution. It uses p/invoke, but seems to work well, 32 or 64 cpu:

/// <summary>
/// A utility class to determine a process parent.
/// </summary>
[StructLayout(LayoutKind.Sequential)]
public struct ParentProcessUtilities
{
    // These members must match PROCESS_BASIC_INFORMATION
    internal IntPtr Reserved1;
    internal IntPtr PebBaseAddress;
    internal IntPtr Reserved2_0;
    internal IntPtr Reserved2_1;
    internal IntPtr UniqueProcessId;
    internal IntPtr InheritedFromUniqueProcessId;

    [DllImport("ntdll.dll")]
    private static extern int NtQueryInformationProcess(IntPtr processHandle, int processInformationClass, ref ParentProcessUtilities processInformation, int processInformationLength, out int returnLength);

    /// <summary>
    /// Gets the parent process of the current process.
    /// </summary>
    /// <returns>An instance of the Process class.</returns>
    public static Process GetParentProcess()
    {
        return GetParentProcess(Process.GetCurrentProcess().Handle);
    }

    /// <summary>
    /// Gets the parent process of specified process.
    /// </summary>
    /// <param name="id">The process id.</param>
    /// <returns>An instance of the Process class.</returns>
    public static Process GetParentProcess(int id)
    {
        Process process = Process.GetProcessById(id);
        return GetParentProcess(process.Handle);
    }

    /// <summary>
    /// Gets the parent process of a specified process.
    /// </summary>
    /// <param name="handle">The process handle.</param>
    /// <returns>An instance of the Process class.</returns>
    public static Process GetParentProcess(IntPtr handle)
    {
        ParentProcessUtilities pbi = new ParentProcessUtilities();
        int returnLength;
        int status = NtQueryInformationProcess(handle, 0, ref pbi, Marshal.SizeOf(pbi), out returnLength);
        if (status != 0)
            throw new Win32Exception(status);

        try
        {
            return Process.GetProcessById(pbi.InheritedFromUniqueProcessId.ToInt32());
        }
        catch (ArgumentException)
        {
            // not found
            return null;
        }
    }
}