<form id="form1" runat="server">
   <div>
    <asp:FileUpload ID="ExcelFileUpload" runat="server" />
    <asp:Button ID="UploadBtn" runat="server" Text="確定上傳" OnClick="UploadBtn_Click" />
   </div>
  </form>

protected void UploadBtn_Click(object sender, EventArgs e)
{
 if (ExcelFileUpload.HasFile == false)//HasFile用來檢查FileUpload是否有文件
 {
  Response.Write("<script>alert('請您選擇Excel文件')</script> ");
  return;//當無文件時,返回
 }
 string IsXls = Path.GetExtension(ExcelFileUpload.FileName).ToString().ToLower();//System.IO.Path.GetExtension獲得文件的擴展名
 if (IsXls != ".xlsx" && IsXls != ".xls")
 {
  Response.Write(ExcelFileUpload.FileName);
  Response.Write("<script>alert('只可以選擇Excel文件')</script>");
  return;//當選擇的不是Excel文件時,返回
 }

 string filename = ExcelFileUpload.FileName;//獲取Execle文件名 
 string savePath = Server.MapPath(("UploadExcel\\") + filename);//Server.MapPath 服務器上的指定虛擬路徑相對應的物理文件路徑
 //savePath ="D:\vsproject\Projects\exceltestweb\exceltestweb\uploadfiles\test.xls"
 //Response.Write(savePath);
 DataTable ds = new DataTable();
 ExcelFileUpload.SaveAs(savePath);//將文件保存到指定路徑

 DataTable dt = GetExcelDatatable(savePath);//讀取excel數據
 List<RegNumInfo> regList = ConvertDtToInfo(dt);//將datatable轉為list
 File.Delete(savePath);//刪除文件

 Response.Write("<script>alert('上傳文件讀取數據成功！');</script>");
}
/// <summary>
/// 從excel文件中讀取數據
/// </summary>
/// <param name="fileUrl">實體文件的存儲路徑</param>
/// <returns></returns>
private static DataTable GetExcelDatatable(string fileUrl)
{
 //支持.xls和.xlsx，即包括office2010等版本的;HDR=Yes代表第一行是標題，不是數據；
 string cmdText = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + fileUrl + "; Extended Properties=\"Excel 12.0;HDR=Yes\"";
 System.Data.DataTable dt = null;
 //建立連接
 OleDbConnection conn = new OleDbConnection(cmdText);
 try
 {
  //打開連接
  if (conn.State == ConnectionState.Broken || conn.State == ConnectionState.Closed)
  {
   conn.Open();
  }

  System.Data.DataTable schemaTable = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
  string strSql = "select * from [Sheet1$]"; //這里指定表明為Sheet1,如果修改過表單的名稱，請使用修改后的名稱
  OleDbDataAdapter da = new OleDbDataAdapter(strSql, conn);
  DataSet ds = new DataSet();
  da.Fill(ds);
  dt = ds.Tables[0]; ;
  return dt;
 }
 catch (Exception exc)
 {
  throw exc;
 }
 finally
 {
  conn.Close();
  conn.Dispose();
 }
}
/// <summary>
/// 將datatable轉換為list集合
/// </summary>
/// <param name="dt">DataTable</param>
/// <returns></returns>
private static List<RegNumInfo> ConvertDtToInfo(DataTable dt)
{
 List<RegNumInfo> list = new List<RegNumInfo>();
 if (dt.Rows.Count > 0)
 {
  foreach (DataRow item in dt.Rows)
  {
   RegNumInfo info = new RegNumInfo();
   info.RegNum = item[0].ToString();
   info.Name = item[1].ToString();
   info.Period = item[2].ToString();
   info.Remark = item[3].ToString();
   list.Add(info);
  }
 }
 return list;
}

public class RegNumInfo
{
 public string RegNum { get; set; }
 public string Name { get; set; }
 public string Period { get; set; }
 public string Remark { get; set; }
}