Metric Converter(Simple Conditions)

using System;

namespace MetricConverter
{
    class Program
    {
        static void Main(string[] args)
        {
            double distance = double.Parse(Console.ReadLine());
            string inputMetric = Console.ReadLine();
            string outputMetric = Console.ReadLine();

            if (inputMetric == "m")
            {
                distance /= 1000;
            }
            else if (inputMetric == "cm")
            {
                distance /= 100000;
            }
            else if (inputMetric == "mm")
            {
                distance /= 1000000;
            }
            else if (inputMetric == "mi")
            {
                distance /= 0.621371192;
            }
            else if (inputMetric == "in")
            {
                distance /= 39370.0787;
            }
            else if (inputMetric == "ft")
            {
                distance /= 3280.8399;
            }
            else if (inputMetric == "yd")
            {
                distance /= 1093.6133;
            }

            if (outputMetric == "m")
            {
                distance *= 1000;
            }
            else if (outputMetric == "cm")
            {
                distance *= 100000;
            }
            else if (outputMetric == "mm")
            {
                distance *= 1000000;
            }
            else if (outputMetric == "mi")
            {
                distance *= 0.621371192;
            }
            else if (outputMetric == "in")
            {
                distance *= 39370.0787;
            }
            else if (outputMetric == "ft")
            {
                distance *= 3280.8399;
            }
            else if (outputMetric == "yd")
            {
                distance *= 1093.6133;
            }

            Console.WriteLine(distance);
        }
    }
}

Решение с тернарен оператор:

using System;

namespace MetricConverter
{
    class Program
    {
        static void Main(string[] args)
        {
            double distance = double.Parse(Console.ReadLine());
            string inputMetric = Console.ReadLine();
            string outputMetric = Console.ReadLine();

            distance /=
                inputMetric == "m" ? 1000 :
                inputMetric == "cm" ? 100000 :
                inputMetric == "mm" ? 1000000 :
                inputMetric == "mi" ? 0.621371192 :
                inputMetric == "in" ? 39370.0787 :
                inputMetric == "ft" ? 3280.8399 :
                inputMetric == "yd" ? 1093.6133 : 1;

            distance *=
                outputMetric == "m" ? 1000 :
                outputMetric == "cm" ? 100000 :
                outputMetric == "mm" ? 1000000 :
                outputMetric == "mi" ? 0.621371192 :
                outputMetric == "in" ? 39370.0787 :
                outputMetric == "ft" ? 3280.8399 :
                outputMetric == "yd" ? 1093.6133 : 1;

            Console.WriteLine(distance);
        }
    }
}

Решение с речник:

using System;
using System.Collections.Generic;

namespace MetricConverter
{
    class Program
    {
        static void Main(string[] args)
        {
            double distance = double.Parse(Console.ReadLine());
            string inputMetric = Console.ReadLine();
            string outputMetric = Console.ReadLine();

            var metricsToKM = new Dictionary<string, double>() {
                { "km", 1 },
                { "m", 1000 },
                { "cm", 100000 },
                { "mm", 1000000 },
                { "mi", 0.621371192 },
                { "in", 39370.0787 },
                { "ft", 3280.8399 },
                { "yd", 1093.6133 }
            };

            Console.WriteLine(distance / metricsToKM[inputMetric] * metricsToKM[outputMetric]);
        }
    }
}