asp.net 读入html文件替换

cs文件：
using System.IO;
string context = "";
string path = HttpContext.Current.Server.MapPath("") + "\\test\\test.html";
 System.Text.Encoding code = System.Text.Encoding.GetEncoding("utf-8");
                StreamReader sr = null;
                try
                {
                    sr = new StreamReader(path, code);
                    context = sr.ReadToEnd();
                    context = context.Replace("<firstname>", "小虫");
                    context = context.Replace("<lastname>", "爬爬");
                    Response.Write(context);
                    sr.Close();
                }
                catch (Exception exp)
                {
                    HttpContext.Current.Response.Write(exp.Message);