添加项目组合框与数据源

Question

我有一个方法（LoadCustomers（）），它返回一个元素字典，如下所示：

Dictionary<int, string>()

我把它连接到这样的组合框的数据源：

             Myclass m = new Myclass();
             combo1.DataSource = new BindingSource(m.LoadCustomers(), null);
             combo1.DisplayMember = "Value";
             combo1.ValueMember = "Key";

现在我想在组合框的列表前放一个像：

这样的项目

             <select one customer>

如何在winforms的c＃中执行此操作？

很多

Answer 1

将此选项添加到客户词典

const int EMPTYCUSTOMERKEY = -1;  //be sure Customers will not contain this value
const string EMPTYCUSTOMERVALUE = "<select one customer>";

Myclass m = new Myclass();
Dictionary<int, string> customerSource = m.LoadCustomers();

customerSource.Add(EMPTYCUSTOMERKEY, EMPTYCUSTOMERVALUE);

combo1.DataSource = new BindingSource(customerSource, null);
combo1.DisplayMember = "Value";
combo1.ValueMember = "Key";