common/Utils/UserAccessCtrl/TemperatureSource.cs

using System;
using System.Runtime.InteropServices;

namespace Xylem.Common.Utils.UserAccessCtrl
{
    public class TemperatureSource : IDisposable
    {
        [DllImport("GMH3x32E.dll")]
        public static extern Int16 UniversalOpenCom(Int16 ini16COMPortNumber, UInt32 inui32BaudRate, Int16 inui16ConverterType, Int16 ini16Parity, Int16 ini16StoppBits);

        [DllImport("GMH3x32E.dll")]
        public static extern Int16 GMH_CloseCom();

        [DllImport("GMH3x32E.dll")]
        unsafe public static extern Int16 GMH_Transmit(Int16 ini16DeviceAddress, Int16 ini16TransmitCode, Int16* refi16ptrPriority, Double* refdblptrFloatValue, Int32* refi32ptrIntegerValue);

        private readonly Boolean connected;

        public TemperatureSource() 
            => connected = UniversalOpenCom(Appsettings.GMHPort, 4800, 8, 0, 0) == 2;

        public Double GetTemperature()
        {
            try
            {
                var result = default(Int16);
                var priority = default(Int16);
                var temperature = double.MinValue;
                var value = default(Int32);

                unsafe
                {
                    result = GMH_Transmit(1, 0, &priority, &temperature, &value);
                }

                if (temperature < 50)
                {
                    return -1.11;
                }
                else if (temperature > 50)
                {
                    return 1.11;
                }

                return temperature;
            }
            catch
            {
                return 0;
            }
        }

        public void Dispose() 
            => GMH_CloseCom();
    }
}