Formatting large numbers in C#

Question

I am using Unity to make an "Incremental Game" also known as an "Idle Game" and I am trying to format large numbers. For example, when gold gets to say 1000 or more, it will display as Gold: 1k instead of Gold: 1000.

using UnityEngine;
using System.Collections;

public class Click : MonoBehaviour {

    public UnityEngine.UI.Text GoldDisplay;
    public UnityEngine.UI.Text GPC;
    public double gold = 0.0;
    public int gpc = 1;

    void Update(){
        GoldDisplay.text = "Gold: " +  gold.ToString ("#,#");
        //Following is attempt at changing 10,000,000 to 10.0M
        if (gold >= 10000000) {
        GoldDisplay.text = "Gold: " + gold.ToString ("#,#M");
        }
        GPC.text = "GPC: " + gpc;
    }

    public void Clicked(){
            gold += gpc;
    }
}

I have tried other examples while searching online, which is where gold.ToString ("#,#"); came from, however none of them worked.

Answer 1

Slight refactoring:

public static string KMBMaker( double num )
{
    double numStr;
    string suffix;
    if( num < 1000d )
    {
        numStr = num;
        suffix = "";
    }
    else if( num < 1000000d )
    {
        numStr = num/1000d;
        suffix = "K";
    }
    else if( num < 1000000000d )
    {
        numStr = num/1000000d;
        suffix = "M";
    }
    else
    {
        numStr = num/1000000000d;
        suffix = "B";
    }
    return numStr.ToString() + suffix;
}

Use:

GoldDisplay.text = KMBMaker(gold);

Changes:

1. Explicitly use double constants
2. Remove duplication
3. Separate concerns - there's no need for this method to know about text boxes

Answer 2

i don't think there is a build-in method for that so i just maybe reinvented the wheel by writing my own way but this should be how i would maybe do it

using System;
using System.Collections.Generic;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            for (double i = 500d; i < 5e23; i *= 100d)
            {
                Console.WriteLine(i.ToMyNumber());
            }

            Console.Read();
        }

    }

    public static class helper
    {
        private static readonly  List<string> myNum;

        static helper()
        {
            myNum = new List<string>();
            myNum.Add("");
            myNum.Add("kilo");
            myNum.Add("mill");
            myNum.Add("bill");
            myNum.Add("tril");
            myNum.Add("quad");
            myNum.Add("quin");
            myNum.Add("sext");
            // ....
        }

        public static string ToMyNumber(this double value)
        {
            string initValue = value.ToString();
            int num = 0;
            while (value >= 1000d)
            {
                num++;
                value /= 1000d;
            }

            return string.Format("{0} {1} ({2})", value, myNum[num], initValue);
        }
    }
}

which print this

500  (500)
50 kilo (50000)
5 mill (5000000)
500 mill (500000000)
50 bill (50000000000)
5 tril (5000000000000)
500 tril (500000000000000)
50 quad (5E+16)
5 quin (5E+18)
500 quin (5E+20)
50 sext (5E+22)

Answer 3

I am using this method in my project, you can use too. Maybe there is better way, I dont know.

public void KMBMaker( Text txt, double num )
    {
        if( num < 1000 )
        {
            double numStr = num;
            txt.text = numStr.ToString() + "";
        }
        else if( num < 1000000 )
        {
            double numStr = num/1000;
            txt.text = numStr.ToString() + "K";
        }
        else if( num < 1000000000 )
        {
            double numStr = num/1000000;
            txt.text = numStr.ToString() + "M";
        }
        else
        {
            double numStr = num/1000000000;
            txt.text = numStr.ToString() + "B";
        }
    }

and use this method in your update like this.

void Update()
{
     KMBMaker( GoldDisplay.text, gold );
}