cannot unselect dropdown list

[Zeng]

Hello,

Does anyone know why setting SelectedIndex to -1 doesn't unselect dropdown
list? Here is my code below. Thank you very much in advance

using (SqlDataReader reader = StoredProcedure.ExecuteReader("ListPeople",
pars))
{
m_peopleDd.DataSource = reader;
m_peopleDd.DataTextField = "UserName";
m_peopleDd.DataValueField = "LoginName";
m_peopleDd.SelectedIndex = -1;
m_peopleDd.DataBind();
}

m_peopleDd.SelectedIndex = -1;