The type or namespace name ‘CrystalReportViewer’ does not exist in the namespace ‘CrystalDecisions.Web’ (are you missing an assembly reference?)

我包含的名称空间是：

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml.Linq;
using MorvelNew.Report;
using System.Data.sql;
using System.Data.sqlClient;
using System.Data.sqlTypes;
using CrystalDecisions.CrystalReports.Engine;
using CrystalDecisions.Web;