Forms Data Controls :: How To Extract Value From A Dropdownlist After Bind 7 Column Name In A Dropdownlist

I have a table and 7 column name.

I bind the 7 column name in one dropdownlist.

Now the problem is,how do I extract the data value in a dropdownlist?

For example,

Dropdownlist contain 7 column name

-subject_name

-subject_code

-venue

-time

-seat_no

-admission_no

-subject_id

when I click the subject_name,I want it to appear in a gridview

Example

Math|9.00-10.00|Hall|18|09090J|...

Below is my current codes which I have a problem.

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
SqlConnection conn = new SqlConnection("Data Source= EN\SQLEXPRESS;" + "Initial Catalog=ms;Integrated Security=SSPI");
SqlDataAdapter adapSel;
string mySQL = "SELECT '" + dd_list.SelectedValue+ "' FROM examtimetable ";
adapSel = new SqlDataAdapter(mySQL, conn);
conn.Open();
DataSet dsSel = new DataSet();
adapSel.Fill(dsSel);
GridView1.DataSource = dsSel;
GridView1.DataBind();
conn.Close();
}
Previously I have bind 7 column name in my dropdownlist
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack == false)
{
SqlConnection conn = new SqlConnection("Data Source= EN\SQLEXPRESS;" + "Initial Catalog=ms;Integrated Security=SSPI");
SqlCommand sqlCmd = new SqlCommand("select column_name from information_schema.columns where table_name='examtimetable' and COLUMN_NAME not like '%ID'", conn);
conn.Open();
SqlDataReader ds;
ds = sqlCmd.ExecuteReader();
dd_list.Items.Clear();
dd_list.DataSource = ds;
dd_list.DataTextField = "Column_Name";
dd_list.DataValueField = "Column_Name";
dd_list.DataBind();
dd_list.Items.Insert(0, "Select Option");
ds.Close();
conn.Close();
}
}