Winform 下拉框绑定问题

public void CmdBind()
        {
            var data = _logic.GetCurrency();//数据源

            if (!data.Any()) return;
            foreach (var currency in data)
            {
                cmdCurrencyName.Items.Add(new CurrencyItem
                {
                    CurrencyName = currency.Description,
                    CurrencyValue = currency.Id
                });
            }
        }

        private void cmdCurrencyName_SelectedIndexChanged(object sender, EventArgs e)
        {
            var selectedItem = (CurrencyItem)cmdCurrencyName.SelectedItem;
            _model.Description = selectedItem.CurrencyName;
            _model.CurrencyId = selectedItem.CurrencyValue;
        }

public class CurrencyItem
        {
            public CurrencyItem()
            { }

            public CurrencyItem(int currencyValue, string currencyName)
            {
                CurrencyValue = currencyValue;
                CurrencyName = currencyName;
            }

            public int CurrencyValue { get; set; }
            public string CurrencyName { get; set; }

            public override string ToString()
            {
                return CurrencyName;
            }
        }