Trim end zero characters for a number string.

TrimEndZero.cs

using System;
using System.Collections.Generic;
using System.Diagnostics.Eventing.Reader;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            var sources = new Dictionary<string, string>()
            {
                ["100"] = "100",
                ["100.000"] = "100",
                ["0.000"] = "0",
                ["0.060800"] = "0.0608",
            };

            foreach (var kv in sources)
            {
                var source = kv.Key;
                var expected = kv.Value;

                Output(source, expected);
            }

            Console.Write("Press any key to exit.");
            Console.ReadKey();
        }

        static void Output(string source, string expected)
        {
            var actual = TrimEndZero(source);
            var indentCount = 12;
            var indent = string.Empty.PadRight(indentCount + 3, ' ');
            var matched = actual == expected;
            Console.WriteLine($"{source.PadRight(indentCount, ' ')} -> {actual}");
            Console.WriteLine($"{indent} {expected}");

            var prevColor = Console.ForegroundColor;
            Console.ForegroundColor = matched ? ConsoleColor.Green : ConsoleColor.Red;
            Console.WriteLine($"{indent} {matched}");
            Console.ForegroundColor = prevColor;
            
            Console.WriteLine();
        }

        static string TrimEndZero(string source)
        {
            var dotPos = -1;
            var trimEndCount = 0;
            var foundNonZero = false;
            var i = source.Length - 1;
            while (i != 0)
            {
                var letter = source[i];
                if (!foundNonZero && letter == '0')
                {
                    trimEndCount++;
                }
                else
                {
                    foundNonZero = true;
                }

                if (letter == '.')
                {
                    dotPos = i;
                }

                i--;
            }

            // example: 100
            if (dotPos < 0)
            {
                return source;
            }

            // example: 100.123
            if (trimEndCount == 0)
            {
                return source;
            }

            var endIndex = source.Length - trimEndCount;
            // example: 100.00
            if (endIndex - 1 == dotPos)
            {
                endIndex--;
            }

            // example: 0.060800
            return source.Substring(0, endIndex);
        }
    }
}