Привязать выделенную запись в DatagridView к текстбоксам и комбобоксу

SqlConnection con = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=C:\\Users\\Elena\\Desktop\\ГОСЫ и ДИПЛОМ\\07.04.2014\\DB1.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True");
        SqlCommand cmd = new SqlCommand();
 
        SqlDataAdapter da = new SqlDataAdapter();
        DataSet ds = new DataSet();
        SqlCommandBuilder cb;
        
        con.Open();
        cmd = new SqlCommand("SELECT Drug.ID_drug AS 'Номер препарата', Drug.Name AS 'Название', Unit_of_measure.Name AS 'Единица измерения' FROM Drug, Unit_of_measure WHERE Drug.ID_unit = Unit_of_measure.ID_unit ", con);
        da = new SqlDataAdapter(cmd);
        da.Fill(ds, "Unit_of_measure, Drug");

            dataGridView1.DataSource = ds;
            dataGridView1.DataMember = "Unit_of_measure, Drug";
 
            textBox1.DataBindings.Add("Text", ds, "Drug.ID_drug");
            textBox2.DataBindings.Add("Text", ds, "Drug.Name");
            comboBox1.DataBindings.Add("Text", ds, "Unit_of_measure.Name");

 textBox1.DataBindings.Add("Text", ds, "Drug.ID_drug",true);

 DataSet ds = new DataSet();
            SqlConnection con = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=C:\\Users\\Elena\\Desktop\\ГОСЫ и ДИПЛОМ\\07.04.2014\\DB1.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True");
 
            con.Open();
            
            SqlDataAdapter drug_adapter = new SqlDataAdapter("Select * FROM Drug", con);
            SqlCommandBuilder drugbuilder;
            drugbuilder = new SqlCommandBuilder(drug_adapter);
 
            SqlDataAdapter unit_adapter = new SqlDataAdapter("Select * FROM Unit_of_measure", con);
            SqlCommandBuilder unitbuilder;
            unitbuilder = new SqlCommandBuilder(unit_adapter);
 
            drug_adapter.Fill(ds, "Drug"); //прочитать Drug
            unit_adapter.Fill(ds, "Unit_of_measure");  // прочитать Unit_of_measure
            con.Close();
 
            ds.Tables["Unit_of_measure"].Columns["Name"].Unique = true;
 
            ds.Relations.Add(new DataRelation("data_rel", ds.Tables["Drug"].Columns["ID_unit"], ds.Tables["Unit_of_measure"].Columns["ID_unit"]));
 
            dataGridView1.DataSource = ds.Tables["Drug"]; // Drug в Датагридвью
            dataGridView1.Columns["ID_unit"].Visible = false; // скрываем колонку с идентификатором
 
            var cbx_unit = new DataGridViewComboBoxColumn(); //добавляем новою колонку
 
            cbx_unit.Name = "Единица измерения";
            cbx_unit.DataSource = ds.Tables["Unit_of_measure"];
            cbx_unit.DisplayMember = "Name";
            cbx_unit.ValueMember = "ID_unit";
            cbx_unit.DataPropertyName = "ID_unit";
            cbx_unit.MaxDropDownItems = 10;
            cbx_unit.FlatStyle = FlatStyle.Flat;
            dataGridView1.Columns.Insert(4, cbx_unit);
            dataGridView1.Columns[4].Width = 200;

ds.Relations.Add(new DataRelation("data_rel", ds.Tables["Unit_of_measure"].Columns["ID_unit"], ds.Tables["Drug"].Columns["ID_unit"]));

DataSet ds = new DataSet();
            SqlConnection con = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=C:\\Users\\Elena\\Desktop\\ГОСЫ и ДИПЛОМ\\07.04.2014\\DB1.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True");
 
            con.Open();
 
            SqlDataAdapter drug_adapter;
            SqlCommand drug_cmd = new SqlCommand("Select * FROM Drug", con);
            drug_adapter = new SqlDataAdapter(drug_cmd);
 
            SqlCommandBuilder drugbuilder;
            drugbuilder = new SqlCommandBuilder(drug_adapter);
 
            SqlDataAdapter unit_adapter;
            SqlCommand unit_cmd = new SqlCommand("Select * FROM Unit_of_measure", con);
            unit_adapter = new SqlDataAdapter(unit_cmd);
 
            SqlCommandBuilder unitbuilder;
            unitbuilder = new SqlCommandBuilder(unit_adapter);