ช่วยหน่อยคับ มันขึ้น Can't perform Create, Update, or Delete operations on 'Table(Expenditure)' because it has no primary key.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Data.Linq;
using System.Transactions;
using System.Text;
using System.Windows.Forms;

namespace Laundry_and_Cleaning_Program
{
    public partial class InsertExpenditure : Form
    {
        public InsertExpenditure()
        {
            InitializeComponent();
        }
        dbExpenditureDataContext db = new dbExpenditureDataContext();
        
        private void button2_Click(object sender, EventArgs e)
        {
            this.Hide();

        }

        private void InsertExpenditure_Load(object sender, EventArgs e)
        {
            ShowData();
            FormatDgvExpenditure();
        }
  
        private void ShowData()
        {
            var ET = from et in db.Expenditures select et;
            
                dgvExpenditureList.DataSource = ET.ToList();
               
        }
        private void FormatDgvExpenditure()
        {
            if (dgvExpenditureList.RowCount > 0)
            {
                dgvExpenditureList.Columns[0].HeaderText = "ลำดับ";
                dgvExpenditureList.Columns[1].HeaderText = "วันเดือนปี";
                dgvExpenditureList.Columns[2].HeaderText = "รายการ";
                dgvExpenditureList.Columns[3].HeaderText = "จำนวนรายจ่าย";
                dgvExpenditureList.Columns[0].Width = 35;
                dgvExpenditureList.Columns[1].Width = 80;
                dgvExpenditureList.Columns[2].Width = 148;
                dgvExpenditureList.Columns[3].Width = 105;
            }
        }

        private void ClearAllData()
        {
            ODET.Text="";
            ExpenditureList.Text = "";
            MoneyExpenditure.Text = "";
            dtp.Value = DateTime.Now;
        }
        private bool CheckExpenditureData()
        {
            if((ExpenditureList.Text.Trim()=="") || (MoneyExpenditure.Text.Trim()==""))
            {
                MessageBox.Show("กรุณาป้อนข้อมูลให้ครบ !!!","ข้อผิดพลาด");
                ExpenditureList.Focus();
                MoneyExpenditure.Focus();
                ExpenditureList.SelectAll();
                MoneyExpenditure.SelectAll();
                return false;
            }
            else{
                return true;
            }
        
        }
        private void dtp_ValueChanged(object sender, EventArgs e)
        {
            dtp.Value = DateTime.Now;
            
            
        }

        private void dgvExpenditureList_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {
            if (e.RowIndex == -1)
            {
                return;
            }
            ODET.Text = dgvExpenditureList.Rows[e.RowIndex].Cells["ODET"].Value.ToString();
            ExpenditureList.Text = dgvExpenditureList.Rows[e.RowIndex].Cells["Ed"].Value.ToString();
            MoneyExpenditure.Text=dgvExpenditureList.Rows[e.RowIndex].Cells["AE"].Value.ToString();
            ExpenditureList.Focus();
            MoneyExpenditure.Focus();
            ExpenditureList.SelectAll();
            MoneyExpenditure.SelectAll();
        }

        private void AddExpenditure_Click_1(object sender, EventArgs e)
        {
            var result = CheckExpenditureData();
            if (result == true)
            {
                Expenditure ep = new Expenditure();
                ep.ED = ExpenditureList.Text;
                ep.AE = MoneyExpenditure.Text;
                ep.PD = dtp.Value.ToString();
                if (MessageBox.Show("คุณต้องการเพิ่มรายจ่ายใหม่ ใช่หรือไม่?", "คำยืนยัน",
                    MessageBoxButtons.YesNo) == System.Windows.Forms.DialogResult.Yes)
                {
                    using (TransactionScope ts = new TransactionScope())
                    {
                        db.Expenditures.InsertOnSubmit(ep);
                        db.SubmitChanges();
                        ts.Complete();
                    }
                    ClearAllData();
                    ShowData();
                    MessageBox.Show("เพิ่มรายจ่ายเรียบร้อยแล้ว", "ผลการทำงาน");
                    ExpenditureList.Focus();
                    MoneyExpenditure.Focus();
                }
            }
       }
   }
}