Dropdown List Value concept

select colu,colu from table 

string k1 = "select Department_Name, Department_id from Department_mast";

        cm = new SqlCommand(k1, cn);

        dr = cm.ExecuteReader();

        ddldeptname.DataSource = dr;

        ddldeptname.DataTextField = "Department_Name";

        ddldeptname.DataValueField = "Department_id";

        ddldeptname.DataBind();

        ddldeptname.Items.Insert(0, "select");

        dr.Close();

Label1.Text = DropDownList1.SelectedItem.Value;

datatexfield

datavaluefield

dl.selecteditem.tex

d1.selecteditem.value