using System;

using System.Linq;

​

// Purpose: see related StackOverflow topic:

// https://stackoverflow.com/a/44633997/1016343

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Sammy".TrimEnd("my"));

        Console.WriteLine("moinmoin gibts gips? gips gibts moin".TrimStart("moin", false));

        Console.WriteLine("moinmoin gibts gips? gips gibts moin".Trim("moin").Trim());

    }

}

​

​

    public static class Extension

    {

        public static string TrimStr(this string str, string trimStr, bool trimEnd = true, bool repeatTrim = true,

            StringComparison comparisonType = StringComparison.OrdinalIgnoreCase)

        {

            int strLen;

            do

            {

                if (!(str ?? "").EndsWith(trimStr)) return str;

                strLen = str.Length;

                {

                    if (trimEnd)

                    {

                        var pos = str.LastIndexOf(trimStr, comparisonType);

                        if ((!(pos >= 0)) || (!(str.Length - trimStr.Length == pos))) break;

                        str = str.Substring(0, pos);

                    }

                    else

                    {

                        var pos = str.IndexOf(trimStr, comparisonType);

                        if (!(pos == 0)) break;

                        str = str.Substring(trimStr.Length, str.Length - trimStr.Length);

                    }

                }

            } while (repeatTrim && strLen > str.Length);

            return str;

        }

        public static string TrimEnd(this string str, string trimStr, bool repeatTrim = true,

            StringComparison comparisonType = StringComparison.OrdinalIgnoreCase) => TrimStr(str, trimStr, true, repeatTrim, comparisonType);

​

        public static string TrimStart(this string str, string trimStr, bool repeatTrim = true,

            StringComparison comparisonType = StringComparison.OrdinalIgnoreCase) => TrimStr(str, trimStr, false, repeatTrim, comparisonType);  

​

        public static string Trim(this string str, string trimStr, bool repeatTrim = true,

            StringComparison comparisonType = StringComparison.OrdinalIgnoreCase) => str.TrimStart(trimStr, repeatTrim, comparisonType).TrimEnd(trimStr, repeatTrim, comparisonType);

​

    }