绑定通用列表<string>到一个组合框

Question

I have a ComboBox and I want to bind a generic List to it. Can anyone see why the code below won't work? The binding source has data in it, but it won't fill the ComboBox data source.

FillCbxProject(DownloadData Down)
{
  BindingSource bindingSource = new BindingSource();
  bindingSource.DataSource = Down.ProjectList;
  cbxProjectd.DataSource = bindingSource;
}

On a side note: Is it bad to pass around an instance of a class?

Thanks!

Answer 1

You need to call the Bind method:

cbxProjectd.DataBind();

If this is for winforms then you need to make sure what you have is being called, the following works:

BindingSource bs = new BindingSource();
bs.DataSource = new List<string> { "test1", "test2" };
comboBox1.DataSource = bs;

Although you can set the ComboBox's DataSource directly with the list.

Answer 2

this is the simple way (it works correctly):

List<string> my_list = new List<string>();
my_list.Add("item 1");
my_list.Add("item 2");
my_list.Add("item 3");
my_list.Add("item 4");
my_list.Add("item 5");
comboBox1.DataSource = my_list;

Answer 3

Here is a rather simple way that doesn't use BindingSource:

first, add the generic list of string, perhaps to a "consts/utils" class:

public static List<string> Months = new List<string>
{
   "Jan",
   "Feb",
   "Mar",
   "Apr",
   "May",
   "Jun",
   "Jul",
   "Aug",
   "Sep",
   "Oct",
   "Nov",
   "Dec"
};

And here's how you add those strings to a combo box:

comboBoxMonth.Items.AddRange(UsageRptConstsAndUtils.Months.ToArray<object>());

Answer 4

BindingSource bs = new BindingSource();
bs.DataSource = getprojectname();
comboBox1 = new ComboBox();
comboBox1.DataSource = bs;

Answer 5

Using Yuriy Faktorovich's code above as a basis, here is how to get a list of dates in LongDateString format for a given number of weeks, and assign them to a combo box. This uses "Monday" but you can simply replace "Monday" with any other DOW to suit your purposes:

private void PopulateSchedulableWeeks()
{
    int WEEKS_COUNT = 13;
    List<String> schedulableWeeks = PlatypusUtils.GetWeekBeginnings(WEEKS_COUNT).ToList();
    BindingSource bs = new BindingSource();
    bs.DataSource = schedulableWeeks;
    comboBoxWeekToSchedule.DataSource = bs;
}

public static List<String> GetWeekBeginnings(int countOfWeeks)
{
    // from http://stackoverflow.com/questions/6346119/datetime-get-next-tuesday
    DateTime today = DateTime.Today;
    // The (... + 7) % 7 ensures we end up with a value in the range [0, 6]
    int daysUntilMonday = ((int)DayOfWeek.Monday - (int)today.DayOfWeek + 7) % 7;
    DateTime nextMonday = today.AddDays(daysUntilMonday);

    List<String> mondays = new List<string>();
    mondays.Add(nextMonday.ToLongDateString());

    for (int i = 0; i < countOfWeeks; i++)
    {
        nextMonday = nextMonday.AddDays(7);
        mondays.Add(nextMonday.ToLongDateString());
    }
    return mondays;
}

...and, if you want to add the actual date to the combo box, too, you can use a Dictionary like so:

    int WEEKS_TO_OFFER_COUNT = 13;
    BindingSource bs = new BindingSource();
    Dictionary<String, DateTime> schedulableWeeks = AYttFMConstsAndUtils.GetWeekBeginningsDict(WEEKS_TO_OFFER_COUNT);             bs.DataSource = schedulableWeeks;
    comboBoxWeekToSchedule.DataSource = bs;
    comboBoxWeekToSchedule.DisplayMember = "Key";
    comboBoxWeekToSchedule.ValueMember = "Value";

public static Dictionary<String, DateTime> GetWeekBeginningsDict(int countOfWeeks)
{
    DateTime today = DateTime.Today;
    // The (... + 7) % 7 ensures we end up with a value in the range [0, 6]
    int daysUntilMonday = ((int)DayOfWeek.Monday - (int)today.DayOfWeek + 7) % 7;
    DateTime nextMonday = today.AddDays(daysUntilMonday);

    Dictionary<String, DateTime> mondays = new Dictionary<String, DateTime>();
    mondays.Add(nextMonday.ToLongDateString(), nextMonday);

    for (int i = 0; i < countOfWeeks; i++)
    {
        nextMonday = nextMonday.AddDays(7);
        mondays.Add(nextMonday.ToLongDateString(), nextMonday);
    }
    return mondays;
}

Answer 6

If anyone finds this necro thread, make sure your list does not contain null items. Otherwise binding will fail silently!

//This will not work!
comboBox1.DataSource = new List<string> { "test1", null, "test2" };

//This is legit!
comboBox1.DataSource = new List<string> { "test1", "", "test2" };