MVC3/4 自定义HtmlHelper截断文本内容(截取)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace System.Web.Mvc //修改为所属System.Web.Mvc命名空间 方便直接使用
{
    /// <summary>
    /// 截取字符串类
    /// </summary>
    public static class CutOfTextExtersions
    {
        /// <summary>
        /// 截取字符串方法
        /// </summary>
        /// <param name="helper"></param>
        /// <param name="str">字符串</param>
        /// <param name="len">长度</param>
        /// <param name="flag">是否显示。。。</param>
        /// <returns></returns>
        public static string GotTopic(this HtmlHelper helper, string str, int len, bool flag)
        {
            if (str != null && str != "")
            {
                string clearstr = str.RemoveHTML();
                int count = 0;
                string strTemp = "";
                for (int i = 0; i < clearstr.Length; i++)
                {
                    if (Math.Abs(((int)(clearstr.Substring(i, 1).ToCharArray())[0])) > 255)
                        count += 2;
                    else
                        count += 1;
                    if (count <= len)
                        strTemp += clearstr.Substring(i, 1);
                    else
                    {
                        strTemp = strTemp + (flag == true ? "…" : "");
                        return str.Replace(clearstr, strTemp);
                    }
                }
                return str.Replace(clearstr, strTemp).Replace("　", "").Trim();
            }
            else
                return "";
        }

        public static string RemoveHTML(this string str)
        {
            try
            {
                if (str != "")
                {
                    str = System.Text.RegularExpressions.Regex.Replace(str, "<[^>]*>", "");
                    str = str.Replace("&nbsp;", " ");
                    return str;
                }
                else
                    return "";
            }
            catch
            {
                return "";
            }
        }
    }
}