程序集发出错误

我收到这样的错误

错误 112 类型或命名空间名称"Repatriation_BO"不能 找到（是否缺少 using 指令或程序集引用？

解决方案是什么？

using System; 
using System.Collections; 
using System.Data; 
using System.ComponentModel; 
using System.Data.SqlClient; 
using System.Web.UI.WebControls; 
using BusinessObject.BusinessObject;
using BusinessLayer.BusinessLayer; 
using System.Text; using System.Reflection; 
using Excel = Microsoft.Office.Interop.Excel; 
using System.Configuration; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.HtmlControls; 
using ParameterPasser; using System.Diagnostics; 
using System.Runtime.InteropServices; 
using System.Web.Security; 
using System.Web.UI.WebControls.WebParts; 
using System.DirectoryServices; 
using System.Net.Mail; 
using System.Drawing; 
using System.Globalization; 
using System.Configuration;  
public partial class ISE_Repatriation : System.Web.UI.Page 
{
   GlobalFunctions gb = new GlobalFunctions();
   Common cs = new Common();    
   CommonBAL cbal = new CommonBAL();     
   public string Urlpage_name;     string lenght_Url;     
   Repatriation_BO repatbo = new Repatriation_BO();     
   Repatriation_BL repatbl = new Repatriation_BL();     
   ISE_Search_BL objISESearch = new ISE_Search_BL();     
   ISEHelper objISE = new ISEHelper();     
   SqlDataReader sdr;