C#-OK按钮不运行，而有'；s没有错误(LINQ到SQL类)

我是C#的新手，我想问为什么按下OK按钮时它不运行？出现错误消息。这是我的表单数据代码，它包含OK按钮：

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;
namespace Bab_8___LINQ_to_SQL_Classes
{
    public partial class DataForm : Form
    {
        Person _temporaryPerson;
        public Person TemporaryPerson {
            get {
                return _temporaryPerson;
            }
        }
        public DataForm()
        {
            InitializeComponent();
            this.Text = "Add New Person";
            _temporaryPerson = new Person();
        }
        public DataForm(Person person)
        {
            InitializeComponent();
            this.Text = "Edit Person Data";
            _temporaryPerson = person;
            txtName.Text = TemporaryPerson.Name;
            txtAddress.Text = TemporaryPerson.Address;
            txtPhone.Text = TemporaryPerson.PhoneNumber;
        }
        private void btnOK_Click(object sender, EventArgs e)
        {
            _temporaryPerson.Name = txtName.Text;
            _temporaryPerson.Address = txtAddress.Text;
            _temporaryPerson.PhoneNumber = txtPhone.Text;
        }
        private void btnCancel_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

然后这是主窗体，它具有LINQ到SQL命令：

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;
namespace Bab_8___LINQ_to_SQL_Classes
{
public partial class Form1 : Form
{
    private AddressbookDBDataContext db;
    public Form1()
    {
        InitializeComponent();
        db = new AddressbookDBDataContext();
        UpdateViewer();
    }
    private void UpdateViewer() {
        dgView.DataSource = (from p in db.Persons select p).ToList();
    }
    private void btnAdd_Click(object sender, EventArgs e)
    {
        DataForm dataForm = new DataForm();
        if (dataForm.ShowDialog() == DialogResult.OK) {
            db.Persons.InsertOnSubmit(dataForm.TemporaryPerson);
            db.SubmitChanges();
            UpdateViewer();
        }
    }
    private void btnEdit_Click(object sender, EventArgs e)
    {
        int selectedIndex = (int)dgView.CurrentRow.Cells[0].Value;
        Person selectedPerson = (from p in db.Persons where p.PersonID == selectedIndex         select p).FirstOrDefault();
        DataForm dataForm = new DataForm(selectedPerson);
        if (dataForm.ShowDialog() == DialogResult.OK) {
            db.SubmitChanges();
            UpdateViewer();
        }
    }
    private void btnDelete_Click(object sender, EventArgs e)
    {
        int selectedIndex = (int)dgView.CurrentRow.Cells[0].Value;
        Person selectedPerson = (from p in db.Persons where p.PersonID == selectedIndex   select p).FirstOrDefault();
        if (MessageBox.Show
            ("Do you want to delete this data?", "Delete Data",
            MessageBoxButtons.OKCancel, MessageBoxIcon.Warning) == DialogResult.OK)
        {
            db.Persons.DeleteOnSubmit(selectedPerson);
            db.SubmitChanges();
            UpdateViewer();
            }
        }
    }
}

我真的希望这个问题能得到解决。

btnOK.DialogResult = DialogResult.OK;