.NET invisible items in combobox

Question

I'm loading Strings to a Combobox -

cboIndexLanguage.Items.Add("ThisLanguage")

i would like to make several of these items invisible.

Answer 1

Try sending a CB_SETMINVISIBLE message for each item.

OR

simply don't set the Text value!

Later edit:

int invItems = 5;
Message msg = new Message();
msg.Msg = CB_SETMINVISIBLE;
msg.LParam = 0;
msg.WParam = invItems;
msg.HWnd = combo.Handle;
MessageWindow.SendMessage(ref msg);

OR invoke this:

[DllImport("user32.dll")]
public static extern int SendMessage(int hWnd, uint Msg, long wParam, long lParam);

Answer 2

you can use an other list to keep strings and show wanted items to user by combo box.To do that you can define a Refresh_Combo_Method that clears combo box items and copies item from list of string to combo , then indexes was in main list.

List<string> colorList = new List<string>();
colorList.Add ("Red");
colorList.Add ("Green");
colorList.Add ("Yellow");
colorList.Add ("Purple");
colorList.Add ("Orange");
...
colorList.Remove("Red");
colorList.Insert(2, "White");
colorList[colorList.IndexOf("Yellow")] = "Black";
colorList.Clear();


...

combobox.Items.Clear();

Answer 3

In thread-safe way you can do it pretty simple (if you only want to play with colors):

private delegate void SetBackColorDelegate(int index, Color color);
private void SetBackColor(int index, Color color)
    {
        if (cboIndexLanguage.InvokeRequired)
        {
            cboIndexLanguage.Invoke(new SetBackColorDelegate(SetBackColor), new object[] { index, color });
        }
        else
        {
            cboIndexLanguage.Items[index].BackColor = color;
        }
    }

In other way, you can just remove items from combo box but save them in some data structure f.ex:

class ComboElement
{
     public String ComboElementText { get; set; }
     public int Index { get; set; }

    public ComboElement(String elementText, int index)
    {
       ComboElementText = elementText;
       Index = index;
    }
}

//* List of hidden elements.
List<ComboElement> hiddenElements = new List<ComboElement>();

then you want to show it again, you can take it from here, and insert into the right place (you know index).

Answer 4

add these to your combobox

class MyCboItem
{
    public bool Visible { get; set; }
    public string Value { get; set; }
    public override string ToString()
    {
        if (Visible) return Value;
        return string.Empty;
    }
}