تقریبا یه همچین چیزی میخواین ؟
private void comboBox1_TextChanged(object sender, EventArgs e)
{
DataSet ds = new DataSet();
SqlDataAdapter objDataAdapter = new SqlDataAdapter("Select LastName From librarian where LastName Like N'" + comboBox1.Text.Trim () + "%'", conn);
objDataAdapter.Fill(ds, "librarian");
DataTable dt = new DataTable();
dt = ds.Tables["librarian"];
dt.DefaultView.RowFilter = "LastName like'%" + comboBox1.Text.Trim() + "%'";
if (dt.DefaultView.Count == 0)
MessageBox.Show("!" + "کلمه ی مورد نظر پیدا نشد ");
comboBox1.DroppedDown = true;
object[] obj = dt.Rows[0].ItemArray;
for (int i = 0; i < obj.Length; i++)
{
comboBox1.Items.Add (obj[i].ToString());
}
dt = null;
}