How can a hashtable be bound to a drop down list?

问题

In vb.net / winforms, how can a hashtable be bound to a drop down list or any other datasource-driven control?

回答1:

Is this winforms, wpf, or asp.net? [update: ahh... winforms ;-p]

winforms wants data to be IList (or, indirectly, via IListSource) - so I'm guessing (from the comment) that you are using winforms. None of the inbuilt dictionary-like collections implement IList, but to be honest it doesn't matter: if you are data-binding, the volume is probably fairly small, so a regular list should be fine.

The best option is something like a List<T> or BindingList<T>, where T has all the properties you want to bind to. Is this an option? If you are stuck with 1.1 (since you mention HashTable rather than Dictionary<,>), then use ArrayList.

Example (in C#):

class MyData
{
    public int Key { get; set; }
    public string Text { get; set; }
}
[STAThread]
static void Main()
{
    var data = new List<MyData>
    {
        new MyData { Key = 1, Text = "abc"},
        new MyData { Key = 2, Text = "def"},
        new MyData { Key = 3, Text = "ghi"},
    };
    ComboBox cbo = new ComboBox
    {
            DataSource = data,
            DisplayMember = "Text",
            ValueMember = "Key"
    };
    cbo.SelectedValueChanged += delegate {
        Debug.WriteLine(cbo.SelectedValue);
    };
    Application.Run(new Form {Controls = {cbo}});
}

回答2:

Just use the dropdown lists's Datasource property

   DropDownList dd = new DropDownList();
   Hashtable mycountries = New Hashtable();
   mycountries.Add("N","Norway");
   mycountries.Add("S","Sweden");
   mycountries.Add("F","France");
   mycountries.Add("I","Italy");
   dd.DataSource=mycountries;
   dd.DataValueField="Key";
   dd.DataTextField="Value";
   dd.DataBind();

回答3:

Example for a given object called Order:

List<Order> list = new List<Order>{};

foreach (Order o in OOS.AppVars.FinalizedOrders.Values)
{
  list.Add(o);
}

this.comboBox_Orders.DataSource = list;
this.comboBox_Orders.DisplayMember = "Description";

What's cool about this is that you can then get the data back out of the list as the original object (not just the value field as in asp.net).

Order order = (Order)this.comboBox_Orders.SelectedValue;

回答4:

Use .tolist. it also works for returned complex types you get from views/stored procedures in entity framework

回答5:

And, if you happen to use Dictionary as the datasource, you can use

MyDDL.Datasouce = myDict.ToList();

and it will convert it to a list type.

回答6:

myCtrl.DataSource = myHashtable
myCtrl.DataBind()

Example source of bindable control:

<itemtemplate>
    <%# DataBinder.Eval(Container.DataItem, "Key", "<td>{0}</td>") %>
    <%# DataBinder.Eval(Container.DataItem, "Value", "<td>${0:f2}</td>") %>
</itemtemplate>

来源：https://stackoverflow.com/questions/298926/how-can-a-hashtable-be-bound-to-a-drop-down-list