ASP.NET: Listbox datasource and databind

问题:

I have an empty listbox on .aspx page

lstbx_confiredLevel1List

I am generating two lists programatically

List<String> l1ListText = new List<string>(); //holds the text 
List<String> l1ListValue = new List<string>();//holds the value linked to the text

I want to load lstbx_confiredLevel1List list box on .aspx page with above values and text. So i am doing following:

lstbx_confiredLevel1List.DataSource = l1ListText;
lstbx_confiredLevel1List.DataTextField = l1ListText.ToString();
lstbx_confiredLevel1List.DataValueField = l1ListValue.ToString();
lstbx_confiredLevel1List.DataBind();

but it does not load the lstbx_confiredLevel1List with l1ListText and l1ListValue.

Any ideas?

回答1:

Why don't you use the same collection as DataSource? It just needs to have two properties for the key and the value. You could f.e. use a Dictionary<string, string>:

var entries = new Dictionary<string, string>();
// fill it here
lstbx_confiredLevel1List.DataSource = entries;
lstbx_confiredLevel1List.DataTextField = "Value";
lstbx_confiredLevel1List.DataValueField = "Key";
lstbx_confiredLevel1List.DataBind();

You can also use an anonymous type or a custom class.

Assuming that you have already these lists and you need to use them as DataSource. You could create a Dictionary on the fly:

Dictionary<string, string> dataSource = l1ListText
           .Zip(l1ListValue, (lText, lValue) => new { lText, lValue })
           .ToDictionary(x => x.lValue, x => x.lText);
lstbx_confiredLevel1List.DataSource = dataSource;

回答2:

You'd better used a dictionnary:

Dictionary<string, string> list = new Dictionary<string, string>();
...
lstbx_confiredLevel1List.DataSource = list;
lstbx_confiredLevel1List.DataTextField = "Value";
lstbx_confiredLevel1List.DataValueField = "Key";
lstbx_confiredLevel1List.DataBind();

回答3:

Unfortunately the DataTextField and DataValueField are not used like that. They are the text representation of the fields they're supposed to show of the current item that's being databound in the DataSource.

If you had an object that held both text and value, you'd make a list of it and set that to datasource like this:

public class MyObject {
  public string text;
  public string value;

  public MyObject(string text, string value) {
    this.text = text;
    this.value = value;
  }
}

public class MyClass {
  List<MyObject> objects;
  public void OnLoad(object sender, EventArgs e) {
    objects = new List<MyObjcet>();
    //add objects
    lstbx.DataSource = objects;
    lstbx.DataTextField = "text";
    lstbx.DataValueField = "value";
    lstbx.DataBind();
  }
}