以下是代码片段：
/// <summary>    
        ///     
        /// </summary>    
        /// <param name="str">待处理的字符串</param>    
        /// <param name="toRep">要替换的字符串中的子串</param>    
        /// <param name="strRep">用来替换toRep字符串的字符串</param>    
        /// <returns>返回一个结果字符串</returns>    
        public static string StringReplace(string str, string toRep, string strRep)
        {
            StringBuilder sb = new StringBuilder();
            int np = 0, n_ptmp = 0;
            for (; ; )
            {
                string str_tmp = str.Substring(np);
                n_ptmp = str_tmp.IndexOf(toRep);

                if (n_ptmp == -1)
                {
                    sb.Append(str_tmp);
                    break;
                }
                else
                {
                    sb.Append(str_tmp.Substring(0, n_ptmp)).Append(strRep);
                    np += n_ptmp + toRep.Length;
                }
            }
            return sb.ToString();
        }