C#-Code

using System;
using System.Collections.Generic;
using System.Linq;

namespace AnalogDiscriminator
{
    class Program
    {
        static void Main(string[] args)
        {
            double m = GetDouble("Masse [kg]: ");
            double h = GetDouble("Groesse [cm]: ") / 100;
            double bmi = m / (h * h);

            Console.WriteLine(string.Format("==> BMI: {0:N2} ({1})", bmi, BMI.Resolve(bmi)));
            Console.ReadLine();
        }

        static double GetDouble(string Text)
        {
            Console.Write(Text);
            string eingabe = Console.ReadLine();
            return Convert.ToDouble(eingabe);
        }

        static class BMI
        {
            static Dictionary<double, string> dict = 
                new Dictionary<double, string>
                {
                    { 0.0, "Starkes Untergewicht" },
                    { 16.0, "Mäßiges Untergewicht" },
                    { 17.0, "Leichtes Untergewicht" },
                    { 18.5, "Normalgewicht " },
                    { 25.0, "Präadipositas" },
                    { 30.0, "Adipositas Grad I" },
                    { 35.0, "Adipositas Grad II" },
                    { 40.0, "Adipositas Grad III" }
                };
            
            internal static string Resolve(double TestKey)
            {
                string retval = string.Empty;
                for (int index = 0; index < dict.Count; index++)
                {
                    KeyValuePair<double,string> item = dict.ElementAt(index);
                    double itemKey = item.Key;
                    string itemValue = item.Value;
                    if (itemKey <= TestKey)
                        retval = itemValue;
                }
                return retval;
            }
        }
    }
}