using System;

public class Program

{

    public static void Main()

    {

        string tmp = "fdfsdf,2222,,3333,";

        //原來的方法

        Console.WriteLine("method1: " + method1(tmp));

        //改寫方法一

        Console.WriteLine("method2: " + method2(tmp));

        //改寫方法二

        Console.WriteLine("method3: " + method3(tmp));

        Console.WriteLine("============================");

        string tmp2 = ",,fdfsdf,2222,,3333,,";

        //原來的方法

        Console.WriteLine("method1: " + method1(tmp2));

        //改寫方法一

        Console.WriteLine("method2: " + method2(tmp2));

        //改寫方法二

        Console.WriteLine("method3: " + method3(tmp2));

    }

    public static string method1(string source)

    {

        var tmpclose = source;

        if (!string.IsNullOrEmpty(tmpclose))

        {

            ////todo  can use tmpclose.TrimStart(",")

            if (tmpclose.IndexOf(',') == 0)

            {

                tmpclose = tmpclose.Substring(1, tmpclose.Length - 1);

            }

            ////todo  can use tmpclose.TrimEnd(",")

            if (tmpclose.LastIndexOf(',') == tmpclose.Length - 1)

            {

                tmpclose = tmpclose.Substring(0, tmpclose.Length - 1);

            }

            if (tmpclose.IndexOf(",,") > 0)

            {

                tmpclose = tmpclose.Replace(",,", ",");

            }

        }

        return tmpclose;

    }

    public static string method2(string source)

    {

        var tmpclose = source;

        if (!string.IsNullOrEmpty(tmpclose))

        {

            //TrimStart => 移除最前頭字元','

            //TrimEnd => 移除最後頭字元','

            //Replace => 替換',,'成','

            tmpclose = tmpclose.TrimStart(',').TrimEnd(',').Replace(",,",",");

        }

        return tmpclose;

    }

    public static string method3(string source)

    {

        var tmpclose = source;

        if (!string.IsNullOrEmpty(tmpclose))

        {

            //以","作分割字串成陣列，把空的陣列移除

            string[] tmp = tmpclose.Split(new string[] {","}, StringSplitOptions.RemoveEmptyEntries);

            //再將陣列加上","轉成字串

            tmpclose = string.Join(",", tmp);

        }

        return tmpclose;

    }

}