C# 字符串操作类

using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;
using System.Text.RegularExpressions;
using System.Security.Cryptography;
/××/
////////////////////////////////////////////////////
///功能：字符文本操作类
///
///
////////////////////////////////////////////////////
namespace XHW
{
    /// <summary>
    /// 字符文本操作类
    /// </summary>
    public class StringHelper
    {
        public static bool IsContains(string[] strs, string value)
        {
            if (strs == null)
            {
                return false;
            }

            foreach (string str in strs)
            {
                if (str == value)
                {
                    return true;
                }
            }

            return false;
        }



        #region 字符串过滤

        #region 对字符串进行HTML编码，针对(input,Textarea)输入时过滤脚本及HTML编码
        /××/
        /// <summary>
        /// 对字符串进行HTML编码，针对(input,Textarea)输入时过滤脚本及HTML编码
        /// </summary>
        /// <param name="source"></param>
        /// <returns></returns>
        #endregion
        public static string EncodeToHtml(string source)
        {
            source = source.Trim();
            source = source.Replace("＇", "＇＇");
            source = source.Replace("\\", "＼");
            source = System.Web.HttpContext.Current.Server.HtmlEncode(source);
            source = source.Replace("\r\n", "<br>");
            source = source.Replace("\n", "<br>");
            return source;
        }


        #region [否决的]对字符串进行HTML编码，针对(input,Textarea)输入时过滤脚本及HTML编码
        /××/
        /// <summary>
        /// [否决的]对字符串进行HTML编码，针对(input,Textarea)输入时过滤脚本及HTML编码 (不符合命名规范，请使用 EncodeToHtml 方法 )
        /// </summary>
        /// <param name="source"></param>
        /// <returns></returns>
        #endregion
        public static string HtmlFilterForInput(string source)
        {
            return EncodeToHtml(source);
        }


        #region 还原HTML编码为字符串,还原HTML编码为字符串，用于返回到input或 Textarea 输入框
        /××/
        /// <summary>
        /// 还原HTML编码为字符串，用于返回到input或 Textarea 输入框
        /// </summary>
        /// <param name="source"></param>
        /// <returns></returns>
        #endregion
        public static string DecodeFormHtml(string source)
        {
            source = source.Trim();
            source = source.Replace("<br>", "\r\n");
            source = source.Replace("<br>", "\n");
            source = System.Web.HttpContext.Current.Server.HtmlDecode(source);
            return source;
        }


        #region [否决的]还原HTML编码为字符串,还原HTML编码为字符串，用于返回到input或 Textarea 输入框
        /××/
        /// <summary>
        /// [否决的]还原HTML编码为字符串，用于返回到input或 Textarea 输入框 (不符合命名规范，请使用 DecodeFormHtml 方法 )
        /// </summary>
        /// <param name="source"></param>
        /// <returns></returns>
        #endregion
        public static string DeHtmlFilterForInput(string source)
        {
            source = source.Trim();
            source = source.Replace("<br>", "\r\n");
            source = source.Replace("<br>", "\n");
            source = System.