原理：
1.判断是否是Excel文件（xls和xlsx两种文件格式，Excel2003和Excle2007）
2.上传Excel文件到服务器的文件夹（要在服务器设置用户ASPNET对此文件夹的读写权限）
3.对此Excel文件进行操作（可以作为OLEdb数据源、ODBC数据源，还可以通过创建Excel.ApplicationClass）

        GridView1.DataSource = null;
        GridView1.DataBind();//先清除GridView1之前的数据绑定
        #region 显示Excel数据
        string clientFilename = FileUpload1.PostedFile.FileName.ToLower();
        string serverFilename = "";
        if (clientFilename == "")
        {
            Label1.Text = "Path and filename can't null！";
            return;
        }
        if (clientFilename.ToLower().IndexOf(".xlsx") > 0)
        {
            serverFilename = ".xlsx";
        }
        else
        {
            if (clientFilename.ToLower().IndexOf(".xls") > 0 && clientFilename.EndsWith("xls"))
            {
                serverFilename = ".xls";
            }
            else
            {
                Label1.Text = "Must be Excel file！";
                return;
            }
        }
        
        serverFilename = "~/upload/" + "Test" + DateTime.Now.Year.ToString()
            + (DateTime.Now.Month > 9 ? DateTime.Now.Month.ToString() : "0" + DateTime.Now.Month.ToString())
            + (DateTime.Now.Day > 9 ? DateTime.Now.Day.ToString() : "0" + DateTime.Now.Day.ToString())
            + (DateTime.Now.Hour > 9 ? DateTime.Now.Hour.ToString() : "0" + DateTime.Now.Hour.ToString())
            + (DateTime.Now.Minute > 9 ? DateTime.Now.Minute.ToString() : "0" + DateTime.Now.Minute.ToString())
            + (DateTime.Now.Second > 9 ? DateTime.Now.Second.ToString() : "0" + DateTime.Now.Second.ToString())
            + DateTime.Now.Millisecond.ToString()+serverFilename;
        
        serverFilename = MapPath(serverFilename);
        if (File.Exists(serverFilename))
        {
            File.Delete(serverFilename);
        }
        FileUpload1.SaveAs(serverFilename);//上传文件

        string strResult = "";
        string strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source='" + serverFilename + "';Extended Properties='Excel 8.0;HDR=YES;'";
        DataTable dt = new DataTable();
        if (serverFilename.ToLower().IndexOf(".xlsx") > 0)
        {
            strConn = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source='" + serverFilename + "';Extended Properties='Excel 12.0;HDR=YES'";
        }
        if (serverFilename.ToLower().IndexOf(".xls") > 0 && serverFilename.EndsWith("xls"))
        {
            strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source='" + serverFilename + "';Extended Properties='Excel 8.0;HDR=YES;'";
        }
        OleDbConnection conn = new OleDbConnection(strConn);
        try
        {
            if (conn.State.ToString() == "Closed")
            {
                conn.Open();
            }
            OleDbDataAdapter adapter = new OleDbDataAdapter("select * from [sheet1$]", strConn);
            adapter.Fill(dt);
            this.GridView1.DataSource = dt;
            GridView1.DataBind();
            conn.Close();
        }
        catch (Exception ee)
        {
            Label1.Text = Label1.Text + " File's content can't matched,please redo it！" + ee.Message;
            //Label1用来显示错误信息
            return;
        }
        #endregion