如何从表格中选择列并从其他表格中自动获取列

Question

我有两个表：教师表和主题表 教师表将教师姓名作为列，而主题表将学科名称作为列，问题是 如何从其组合框中的教师表中选择教师姓名，以及如何从其组合框中的主题表中自动获取所选教师的主题。 注意：当我尝试时，我在老师组合框中得到了老师的名字和学科的名字 ，所以          如何使用c＃在组合框中将它们分开。

enter code here

    private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
    {
        Variable_Attendence();
        Attendence.Select_Teacher_By_TeacherName();

    }

    private void Attendnce_Load(object sender, EventArgs e)
    {
        fill_Teacher_Name_in_Att();
    }
    void Variable_Attendence()
    {
        Attendence.S_Teacher_Name = COMX_Teacher.Text;
        Attendence.S_Subject_Name = COMX_Subjct.Text;
        Attendence.S_Branch_Name = COMX_Branch.Text;
        Attendence.S_Semester_Name = COMX_Semester.Text;
    }

    void fill_Teacher_Name_in_Att()
    {
        Attendence.Fill_Teacher_Att();
        COMX_Teacher.Items.Clear();
        COMX_Subjct.Items.Clear();
        for (int i = 0; i < Attendence.ARL_Teacher_Name.Count; i++)
        {

        COMX_Teacher.Items.Add(Attendence.ARL_Teacher_Name[i].ToString());

        }
    }
      //fill_Teacher
    public void Fill_Teacher_Att()
    {
        try
        {
            DB.OpenDatabase();
            DB.Cmd = new SqlCommand("select Teacher_Name,Subject_Name from 
               TB_Teacher T,TB_Subject sub  where 
               T.Subject_ID=sub.Subject_ID  ", DB.Cn);
            DB.read = DB.Cmd.ExecuteReader();
            ARL_Teacher_Name.Clear();
            ARL_Subject_Name.Clear();



            if (DB.read.HasRows)
            {

                while (DB.read.Read())
                {
                    ARL_Teacher_Name.Add(DB.read["Teacher_Name"]);
                    ARL_Teacher_Name.Add(DB.read["Subject_Name"]);





                }
            }
            else
            {
                ARL_Teacher_Name.Add("Empty");
                ARL_Subject_Name.Add("Empty");

            }

            DB.CloseDatabase();

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
            return;
        }
    }

       // fill Teacher_by_useing_name
    public void Select_Teacher_By_TeacherName()
    {
        try
        {
            DB.OpenDatabase();
            DB.Cmd = new SqlCommand("select Teacher_ID from TB_Teacher 
                     where Teacher_Name = '" + S_Teacher_Name + "' ", 
                              DB.Cn);
            DB.read = DB.Cmd.ExecuteReader();
            if (DB.read.HasRows)
            {

                while (DB.read.Read())
                {
                    Teacher_ID = Convert.ToInt32(DB.read["Teacher_ID"]);

                }
            }
            else
            {

                Teacher_ID = 0;
            }

            DB.CloseDatabase();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
            return;
        }

    }