i am try to get db values to my combo box ,then i need a Read() method but i can't get that....plz help meeee?

string SQL = " SELECT TableColoumName From TableName " ;
DataTable dt = DataManager.ExecuteQuery(SQL);
if (dt.Rows.Count; 0)
{
  comboBox1.DataSource = dtPaymentPurpose;
  comboBox1.DisplayMember = TableColoumName;
  comboBox1.ValueMember = TableColoumName;
  comboBox1.SelectedIndex = -1;
}
else
{
  comboBox1.DataSource = null;
}