未处理 System.Data.OleDb.OleDbException
  Message="找不到文件 'D:\\My Documents\\Visual Studio 2005\\Projects\\student\\student\\bin\\Debug\\student.mdb'。"
private void button1_Click(object sender, EventArgs e)
        {     //连接字符串
            string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;User Id=Admin;Jet OLEDB:Database Password=;Data Source=student.mdb";

            //SQL语句
            string strSql = @"select * from users where username='" + this.textBox1.Text + "' and pwd='" + this.textBox3.Text + "'";

            //创建连接对象，用来建立与数据库的连接通信
            OleDbConnection connection = new OleDbConnection(connectionString);

            //打开连接对象
            connection.Open();

            //创建数据适配器对象
            OleDbDataAdapter command = new OleDbDataAdapter(strSql, connection);

            //数据集对象，存放查询结果
            DataSet ds = new DataSet();

            //用适配器来完成数据集填充
            command.Fill(ds, "users");

            //关闭连接对象