C#，用户代码未处理NullReferenceException？高手帮忙！

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;
using System.IO;namespace 车库管理系统
{
    public partial class Form1 : Form
    {
        private DataSet dsnew;
        private OleDbCommand command = new OleDbCommand();
        private OleDbConnection connection;
        private OleDbDataAdapter adapter;
        private DataTable thetable = new DataTable();
        public Form1()
        {
            InitializeComponent();
        }
        public int a = 0;        private void 信息BindingNavigatorSaveItem_Click(object sender, EventArgs e)
        {
            this.Validate();
            this.信息BindingSource.EndEdit();
            this.信息TableAdapter.Update(this.userDataSet.信息);        }
        private void Form1_Load(object sender, EventArgs e)
        {
            // TODO: 这行代码将数据加载到表“userDataSet.信息”中。您可以根据需要移动或移除它。
            this.信息TableAdapter.Fill(this.userDataSet.信息);
        }        private void pictureBox1_Click(object sender, EventArgs e)
        {
            this.textBox8.Text = "请输入停车卡号关键字";
            this.textBox8.Focus();
            textBox8.SelectAll();
            a = 1;        }
        private void pictureBox2_Click(object sender, EventArgs e)
        {
            this.textBox8.Text = "请输入车主姓名关键字";
            a = 2;
            this.textBox8.Focus();
            textBox8.SelectAll();        }
        private void pictureBox5_Click(object sender, EventArgs e)
        {
            Form2 f2 = new Form2();       //返回
            f2.Show();
            this.Hide();
        }        private void button2_Click(object sender, EventArgs e)
        {
            if (a == 0)
            {
                MessageBox.Show("请选择查询条件!");
                textBox8.Focus();
                textBox8.SelectAll();
            }
            if (a == 1)
            {
                string con = "Select * from 信息 where 停车卡号 like '%" + textBox8.Text + "%'";
                connection = new OleDbConnection();
                connection.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=E:\\车库管理系统\\user.mdb";
                connection.Open();
                command.Connection = connection;
                command.CommandType = CommandType.Text;
                command.CommandText = con;
                adapter = new OleDbDataAdapter("Select * From 信息", connection);
                adapter.SelectCommand = command;
                dsnew = new DataSet();
                adapter.Fill(dsnew, "user");
                thetable = dsnew.Tables["user"];
                信息DataGridView.DataSource = thetable;
            }
            if (a == 2)
            {
                string con = "Select * from 信息 where 车主姓名 like '%" + textBox8.Text + "%'";
                connection = new OleDbConnection();
                connection.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=E:\\车库管理系统\\user.mdb";
                connection.Open();
                command.Connection = connection;
                command.CommandType = CommandType.Text;
                command.CommandText = con;
                adapter = new OleDbDataAdapter("Select * From 信息", connection);
                adapter.SelectCommand = command;
                dsnew = new DataSet();
                adapter.Fill(dsnew, "user");
                thetable = dsnew.Tables["user"];
                信息DataGridView.DataSource = thetable;
            }
            
        }        private void button3_Click(object sender, EventArgs e)
        {
            Form1 f1 = new Form1();
            f1.Show();
            this.Hide();
        }        private void button4_Click(object sender, EventArgs e)
        {
            if (MessageBox.Show("你确定删除吗？", "提示", MessageBoxButtons.YesNo) == DialogResult.Yes)
                信息DataGridView.Rows.RemoveAt(信息DataGridView.SelectedRows[0].Index);
            else
            {
                Form1 f1 = new Form1();
                f1.Show();
                this.Hide();
            }
        }        private void 信息DataGridView_CurrentCellChanged(object sender, EventArgs e)
        {   
            //信息DataGridView内容显示到textbox里，可是加入这个事件之后，进行查询、删除的操作就无法调试通过了，提示（this.textBox2.Text = this.信息DataGridView.CurrentRow.Cells[0].Value.ToString(); “未将对              象引用设置到对象的实例”。）            this.textBox2.Text = this.信息DataGridView.CurrentRow.Cells[0].Value.ToString();   
            this.textBox3.Text = this.信息DataGridView.CurrentRow.Cells[1].Value.ToString();
            this.textBox4.Text = this.信息DataGridView.CurrentRow.Cells[2].Value.ToString();
            this.textBox5.Text = this.信息DataGridView.CurrentRow.Cells[3].Value.ToString();
            this.textBox6.Text = this.信息DataGridView.CurrentRow.Cells[4].Value.ToString();
            this.textBox7.Text = this.信息DataGridView.CurrentRow.Cells[5].Value.ToString();
        }    }
}