ค้นหาข้อมูลตามวันที่ไม่ได้ ใช้ C# กับ Microsoft Access 2007 ครับ

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.Data.OleDb; 

namespace Telephone
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        OleDbConnection Conn;
        OleDbCommand com;
       // OleDbTransaction tr;
        StringBuilder sb = new StringBuilder();
        DataSet ds = new DataSet();

        string strConn; 

        private void Form1_Load(object sender, EventArgs e)
        {
            strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\\CALLDATA.mdb"; 
                
            Conn = new OleDbConnection();
            {
                if (Conn.State == ConnectionState.Open)
                {
                    Conn.Close();
                }
                Conn.ConnectionString = strConn;
                Conn.Open();

               DateTime Today = DateTime.Today;
                DtpStart.Value = Today.AddYears(-1);
                DtpEnd.Value = Today.AddYears(0);



 
            }



        }

        private void btnSearch_Click(object sender, EventArgs e)
        {
            showdata();
        }
        private void showdata()
        {
            DateTime dateBegin = DtpStart.Value;
            DateTime dateFinish = DtpEnd.Value;


            sb.Remove(0, sb.Length);

                sb.Append("SELECT EXTENSION,  ");
                sb.Append("sum(iif(month(STARTDATE)=1,AUTHCHARGE,0)) as [JAN],");
                sb.Append("sum(iif(month(STARTDATE)=2,AUTHCHARGE,0)) as [FEB],");
                sb.Append("sum(iif(month(STARTDATE)=3,AUTHCHARGE,0)) as [MAR],");
                sb.Append("sum(iif(month(STARTDATE)=4,AUTHCHARGE,0)) as [APR],");
                sb.Append("sum(iif(month(STARTDATE)=5,AUTHCHARGE,0)) as [MAY],");
                sb.Append("sum(iif(month(STARTDATE)=6,AUTHCHARGE,0)) as [JUN],");
                sb.Append("sum(iif(month(STARTDATE)=7,AUTHCHARGE,0)) as [JUL],");
                sb.Append("sum(iif(month(STARTDATE)=8,AUTHCHARGE,0)) as [AUG],");
                sb.Append("sum(iif(month(STARTDATE)=9,AUTHCHARGE,0)) as [SEP],");
                sb.Append("sum(iif(month(STARTDATE)=10,AUTHCHARGE,0)) as [OCT],");
                sb.Append("sum(iif(month(STARTDATE)=11,AUTHCHARGE,0)) as [NOV],");
                sb.Append("sum(iif(month(STARTDATE)=12,AUTHCHARGE,0)) as [DEC],");
                sb.Append("sum(AUTHCHARGE) as TOTAL");
        
                sb.Append(" FROM CopyCALLDATA ");
           
            sb.Append  (" WHERE STARTDATE BETWEEN #" + dateBegin + "# AND #" + dateFinish + "#");
                sb.Append(" GROUP BY EXTENSION ");
                string sqlCustomer = sb.ToString();

            OleDbDataReader dr;
            DataTable dt;

            com = new OleDbCommand();
            {
                com.CommandType = CommandType.Text;
                com.CommandText = sqlCustomer;
                com.Connection = Conn;
                dr = com.ExecuteReader();
                if (dr.HasRows)
                {
                    dt = new DataTable();
                    dt.Load(dr);
                    myDgv.DataSource = dt;
                }
                else
                {
                    myDgv.DataSource = null;
                }
            }
            dr.Close();
        }
    }
}