WSUniversalLib/Calculation.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WSUniversalLib
{
    public class Calculation
    {
        public static int GetQuantityForProduct(int productType, int materialType, int count, float width, float length)
        {

            if (count <= -1)
            {
                throw new ArgumentException("Количество меньшу нуля");
            }

            if(width <= -1)
            {
                throw new ArgumentException("Ширина меньше нуля");
            }

            if (length <= -1)
            {
                throw new ArgumentException("Длина меньше нуля");
            }

            double sqaure = width * length;
            double quantity;

            switch(productType)
            {
                case 1:
                    quantity = sqaure * 1.1;
                    break;
                case 2:
                    quantity = sqaure * 2.5;
                    break;
                case 3:
                    quantity = sqaure * 8.43;
                    break;
                default:
                    return -1;
                    break;
            }

            quantity = quantity * count;

            switch(materialType) 
            {
                case 1:
                    quantity = quantity * 1.003;
                    break;
                case 2:
                    quantity = quantity * 1.0012;
                    break;
                default:
                    return -1;
                    break;
            }

            return Convert.ToInt32(Math.Ceiling(quantity));
        }
    }
}