父列表的子集列表未绑定到Winforms中的列表框

Question

I am trying to bind a List of a custom class to a Listbox and cannot get anything to display. The List is a subset of another List. I can bind the parent List and see the items, but not the child List. How can I get the subset List to bind to the Listbox? I have tried changing the order of the ListBox's DisplayMember, ValueMember, and DataSource properties. In debugging I can see that the DataSource has the correct values, but I can't get them to display. Relevant code below:

public class DimZone
{
    public int Zone_Key { get; set; }
    public int Zone_ID { get; set; }
    public int Facility_Key { get; set; }
    public string Zone_Name { get; set; }
    public string Zone_Type { get; set; }
}

GlobalVariables Class containing global List collection:

public static List<DimZone>[] zoneCollection = new List<DimZone>[maxServerCount];

Form using global List collection and subset List:

List<DimZone> zoneCollectionAppended = new List<DimZone>();

private void StaffStatusReportForm_Load(object sender, EventArgs e)
    {
        facilityComboBox.DataSource = GlobalVariables.facilityCollection;
        GetFacilityIndex();
        CreateZoneAppendedList();
        PopulateUI();
    }

private void CreateZoneAppendedList()
    {
        foreach (var zone in GlobalVariables.zoneCollection[currentFacilityIndex])
        {
            if (zone.Zone_Name != "All")
            {
                zoneCollectionAppended.Add(zone);
            }
        }
    }

private void PopulateUI()
    {
        if (zoneCollectionAppended != null)
        {
            zoneListBox.DisplayMember = "Zone_Name";
            zoneListBox.ValueMember = "Zone_ID";
            zoneListBox.DataSource = zoneCollectionAppended;
        }
    }

Answer 1

Your code contains various unclear parts. In any case, the best proceeding in these situations is setting up a properly-working simpler code and modifying it until reaching the stage you want. I can provide this properly-working first step. Sample code:

private void Form1_Load(object sender, EventArgs e)
{
    List<DimZone> source = new List<DimZone>();
    DimZone curZone = new DimZone() { Zone_Key = 1, Zone_ID = 11, Facility_Key = 111, Zone_Name = "1111", Zone_Type = "11111" };
    source.Add(curZone);
    curZone = new DimZone() { Zone_Key = 2, Zone_ID = 22, Facility_Key = 222, Zone_Name = "2222", Zone_Type = "22222" };
    source.Add(curZone);

    zoneListBox.DisplayMember = "Facility_Key";
    zoneListBox.DataSource = source;
}

public class DimZone
{
    public int Zone_Key { get; set; }
    public int Zone_ID { get; set; }
    public int Facility_Key { get; set; }
    public string Zone_Name { get; set; }
    public string Zone_Type { get; set; }
}

Try this code and confirm that the changes in zoneListBox.DisplayMember (eg, "Zone_Key" , "Zone_ID" , etc.) are immediately reflected in the values being displayed by zoneListBox .

Answer 2

The problem was I was changing zoneListBox.DataSource from one source to another on load, which caused the error. In order for the DataSource to update properly, I had to set zoneListBox.DataSource = null before updating to a new DataSource. I don't know why I have to set it to null first, but it solved my problem. So my updated code is as follows:

private void PopulateUI()
{
    if (zoneCollectionAppended != null)
    {
        zoneListBox.DisplayMember = "Zone_Name";
        zoneListBox.ValueMember = "Zone_ID";

        //DataSource had to be reset to null before updating to new DataSource
        zoneListBox.DataSource = null;

        zoneListBox.DataSource = zoneCollectionAppended;
    }
}