namespace Day04_001事務
{
    class Program
    {
        static void Main(string[] args)
        {
            string str = "Data Source=.;Initial Catalog=MySchool;Integrated Security=True";
            string sql="insert into grade (gradename) values ('S2226')";
            using (SqlConnection conn=new SqlConnection(str))
            {
                SqlCommand cmd=new SqlCommand(sql,conn);
                conn.Open();
                SqlTransaction tran = conn.BeginTransaction();
                cmd.Transaction = tran;
                try
                {
                    int count = cmd.ExecuteNonQuery();
                    if (count > 0)
                    {
                        Console.WriteLine("add ok");
                    }
                    tran.Commit();
                }
                catch (Exception)
                {
                    
                   tran.Rollback();
                }
                }
            Console.ReadKey();

        }
    }
}
 

namespace using釋放資源
{
    class Program
    {
        static void Main(string[] args)
        {
            string sql="select * from student";
            using (SqlConnection conn = new SqlConnection(SqlHelper.constr))
            {
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    conn.Open();
                    Console.WriteLine("高傲的分割線");
                    Console.WriteLine("資料庫");                    
                }
            }
            Console.ReadKey();
        }
    }
}
 

namespace Day05_001實體類的高階應用
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            string str = "Data Source=.;Initial Catalog=MySchool;Integrated Security=True";
            SqlConnection con=new SqlConnection(str);
            string sql="select * from grade";
            SqlDataAdapter da=new SqlDataAdapter(sql,con);
            DataSet ds=new DataSet();
            da.Fill(ds, "gradeinfo");
            comboBox1.DataSource = ds.Tables[0];
            comboBox1.ValueMember = "gradeid";
            comboBox1.DisplayMember = "gradename";
        }

        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            string str = "Data Source=.;Initial Catalog=MySchool;Integrated Security=True";
            string gradename = comboBox1.Text;
            int gradeid = GetIdByName(gradename);
            SqlConnection con=new SqlConnection(str);
            string sql = "select * from subject where 
 
[email protected]";
            SqlParameter para=new SqlParameter("@gradeid",gradeid);
            SqlCommand cmd=new SqlCommand(sql,con);
            cmd.Parameters.Add(para);
            SqlDataAdapter da=new SqlDataAdapter();
            da.SelectCommand = cmd;
            DataSet ds=new DataSet();
            da.Fill(ds, "subjectinfo");
            comboBox2.DataSource = ds.Tables["subjectinfo"];
            comboBox2.ValueMember = "subjectid";
            comboBox2.DisplayMember = "subjectname";
            if (ds.Tables["subjectinfo"].Rows.Count == 0)
            {
                ds.Tables["subjectinfo"].Clear();
            }
        }
        //根據id獲取年級名稱
        private int GetIdByName(string gradename)
        {
            string str = "Data Source=.;Initial Catalog=MySchool;Integrated Security=True";
            SqlConnection con = new SqlConnection(str);
            string sql = "select gradeid from grade where gradename='" + gradename + "'";
            SqlCommand cmd=new SqlCommand(sql,con);
            con.Open();
            int gradeid = Convert.ToInt32(cmd.ExecuteScalar());
            con.Close();
            return gradeid;
        }

        //根據id獲取科目名稱
        public int GetidByName(string subjectname)
        {
            string str = "Data Source=.;Initial Catalog=MySchool;Integrated Security=True";
            SqlConnection con = new SqlConnection(str);
            string sql = "select subjectid from subject where subjectname='" + subjectname + "'";
            SqlCommand cmd = new SqlCommand(sql, con);
            con.Open();
            int gradeid = Convert.ToInt32(cmd.ExecuteScalar());
            con.Close();
            return gradeid;
        }
        public DataTable StudentInfo(int gradeid, int subjectid )
        {
            string str = "Data Source=.;Initial Catalog=MySchool;Integrated Security=True";
            string sql = @"select  student.StudentNo, LoginPwd, StudentName, Gender, student.gradeid, Phone, Address, Birthday, Email from student, result,subject
                          where subject.subjectid=result.subjectid and [email protected] and [email protected] ";
            using (SqlConnection con = new SqlConnection(str))
            {
                SqlParameter[] paras = 
                  {
                      new SqlParameter("@gradeid",gradeid),                     
                      new SqlParameter("@subjectid",subjectid)                  
                  };
                SqlCommand cmd = new SqlCommand(sql, con);
                cmd.Parameters.AddRange(paras);
                con.Open();
                SqlDataAdapter Adapter = new SqlDataAdapter();
                Adapter.SelectCommand = cmd;
                DataSet da = new DataSet();
                Adapter.Fill(da, "pp");
                return da.Tables["pp"];
            }

        }

        private void button1_Click(object sender, EventArgs e)
        {
            string gradename = comboBox1.Text;
            int gradeid = GetIdByName(gradename);
            string subjectname = comboBox2.Text;
            int subjectid = GetidByName(gradename);
            dataGridView1.DataSource = StudentInfo(gradeid, subjectid);
        }

    }
}