2 ushort remix to 1 int, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            
            // Lecture de l'état des zones
            const int addrDebut = 13; // Adresse debut dans le buffer pour un COM
            const int taillePlage = 7; // Définit la taille de la plage à scruter

ushort[] arrLect = new ushort[taillePlage];
            // Intrusion
            // 0: Zone 01 -> 16
            // 1: Zone 17 -> 32
            // 2: Zone 33 -> 48
            // 3: Zone 49 -> 64
            // 4: Zone 65 -> 80
            // 5: Zone 81 -> 96
            // 6: Zone 97 -> 112

arrLect[0] = 10;
            arrLect[1] = 65535;
            arrLect[2] = 65535;
            arrLect[3] = 65535;
            arrLect[4] = 65535;
            arrLect[5] = 65535;
            arrLect[6] = 65535;

for (int numVarIntr = 1; numVarIntr <= 4; numVarIntr++) // Incrémente nom var sortie
            {
                int val = 0;
                for (int indexZone = 1; indexZone <= 16; indexZone++) // 
                {
                    // Détermine l'index du bit en fonction de la zone
                    int indexBIT = indexZone + 7; // Gestion de l'inversion poids faible / poids fort
                    if (indexZone > 8)
                        indexBIT = indexZone - 9;
                    
                    // Réorganise les bits de la variable
                    ushort mask = (ushort)(1 << indexBIT);
                    
                    int arrIndex = numVarIntr*2-2;
                    val |= arrLect[arrIndex] & mask;
                    
                    arrIndex++; 
                    if(arrIndex<(taillePlage-1))
                    {
                        val |= (arrLect[arrIndex] & mask) << 16;
                    }
                }
                
                // Ecriture de la variable
                Console.WriteLine( "" );
                Console.WriteLine( "numVarIntr: " + numVarIntr.ToString() );
                Console.WriteLine( "BIN: " + "| 7|| 6|| 5|| 4|| 3|| 2|| 1|| 0|");
                Console.WriteLine( "BIN: " + Convert.ToString(val, 2).PadLeft(32, '0') + " - DEC: " + val.ToString() );
            }
            
            
    
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,12 sec, absolute running time: 0,09 sec, cpu time: 0,08 sec, average memory usage: 14 Mb, average nr of threads: 3, absolute service time: 0,27 sec