Iprincipal myprincipal = this.user 出现异常

Iprincipal myprincipal = this.user 出现错误
protected void btnsubmit_click(object sender, EventArgs e)
  {
  Iprincipal myprincipal = this.User; 是错的吗？
  string tablestring = "<table border=1><tr><td>Name</td><td>";
  tablestring += Server.HtmlEncode(myprincipal.identity.name) + "</td></tr>";
  Response.Write(tablestring);
  }

------解决方案--------------------------------------------------------
路过,up