try this
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack)
{
Bugtracker objddl=new Bugtracker();
DataSet ds = objddl.GetTeamMember();
DropDownList1.DataSource = ds;
DropDownList1.DataTextField = "TM_Name";
DropDownList1.DataBind();
}
}
for any query hit to replay.