vs2008 C#控制excel错误

peng3726

错误        1        类型“Microsoft.Office.Interop.Excel.Application”同时存在于“c:\Windows\assembly\GAC\Microsoft.Office.Interop.Excel\11.0.0.0__71e9bce111e9429c\Microsoft.Office.Interop.Excel.dll”和“c:\Program Files (x86)\Microsoft Visual Studio 9.0\Visual Studio Tools for Office\PIA\Office12\Microsoft.Office.Interop.Excel.dll”中        C:\Users\Administrator\Documents\Visual Studio 2008\Projects\WindowsFormsApplication3\WindowsFormsApplication3\Form1.cs        17        40        WindowsFormsApplication3


using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using office = Microsoft.Office.Core;
using Microsoft.Office.Interop.Excel;



引用就添加了3个，但是就出现这个错误，这是为什么？