过滤上传文件的扩展名

/**/ /// <summary>        /// 取文件的扩展名：例如：aspx ,asp  ,asa  .......        /// </summary>        /// <param name="strOriginal"></param>        /// <param name="strSymbol"></param>        /// <returns></returns>          public   string  GetLastStr( string  strOriginal, string  strSymbol)         ... {            int strPlace=strOriginal.LastIndexOf(strSymbol)+strSymbol.Length;            strOriginal=strOriginal.Substring(strPlace);            return strOriginal;        }          /**/ /// <summary>        /// 事件        /// </summary>        /// <param name="sender"></param>        /// <param name="e"></param>          private   void  Button1_Click( object  sender, System.EventArgs e)         ... {            try            ...{                string noFile = "aspx|asp|asa|exe|dll|js|vbs|bat|htm|html|shtml|xhtml";                  string strname = GetLastStr(File1.PostedFile.FileName,".");                int n =noFile.IndexOf(strname.ToLower());                if(noFile.IndexOf(strname.ToLower()) >= 0)                ...{                    Response.Write("<script>alert(' 请不要上传非法文件....')</script>");                }            }            catch(System.Exception er)            ...{                Response.Write("<font color=red>"+er.Message+"</font>");            }        }