DataSource Controls :: Incorrect Syntax Near The Keyword "and"

this is my code for binding a gridview on based of two dropdownlists selected choices.

protected void Bind_NBD()
{
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["contest"].ConnectionString);
con.Open();
StringBuilder sub = new StringBuilder("select * from mtblNBD where (1=1)
order by Deadline desc");
SqlCommand com = new SqlCommand(sub.ToString(), con);
if (ddlDivision.SelectedValue != "0")
{
sub.Append(" and Division = @Division");
com.CommandText = sub.ToString();
com.Parameters.AddWithValue("@Division", ddlDivision.SelectedItem.Text);
;
}
if (ddlGroup.SelectedValue != "0")
{
sub.Append(" and GroupIn=@GroupIn");
com.CommandText = sub.ToString();
com.Parameters.AddWithValue("@GroupIn", ddlGroup.SelectedItem.Text);
}
SqlDataAdapter da = new SqlDataAdapter(com);
DataTable dt = new DataTable();
da.Fill(dt);
if (dt.Rows.Count > 0)
{
GridView1.DataSource = dt;

if in this query StringBuilder sub = new StringBuilder("select * from mtblNBD where (1=1) order by Deadline desc"); I remove the bolded part "order by Deadline desc" then it works good. but with this part the result is with an error. Incorrect syntax near the keyword 'and'. what causes the error.