using System;

​

// 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("Sammy".TrimStart("Sam"));

        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

        {

            strLen = str.Length;

            {

                if (trimEnd)

                {

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

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

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

                    str = str.Substring(0, pos);

                }

                else

                {

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

                    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;

    }

​

    // the following is C#6 syntax, if you're not using C#6 yet

    // replace "=> ..." by { return ... }

​

    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);

​

}