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