DropdownList DataSource

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.

1. DataSource – Name of the dataset or datatable or your datasource
2. DataValueField – These field will be hidden
3. DataTextField – These field will be displayed on the dropdwon.

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..............
}