You can bind the DropDownList in different ways by using List, Dictionary, Enum, DataSet DataTable.
Main you have to consider three thing while binding the datasource of a dropdown.
you can use following code to bind a dropdownlist to a datasource as a datatable:
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString);
SqlCommand cmd = new SqlCommand("Select * from tblQuiz", con);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt=new DataTable();
da.Fill(dt);
DropDownList1.DataTextField = "QUIZ_Name";
DropDownList1.DataValueField = "QUIZ_ID"
DropDownList1.DataSource = dt;
DropDownList1.DataBind();
if you want to process on selection of dropdownlist, then you have to change AutoPostBack="true" you can use SelectedIndexChanged event to write your code.
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
string strQUIZ_ID=DropDownList1.SelectedValue;
string strQUIZ_Name=DropDownList1.SelectedItem.Text;
// Your code..............
}