ListBox Help

Question

Hi people first post here =] I have a C#.Net program that has 3 forms ( frmMain frmPrint frmAudio.) Each of the three forms have a listbox frmPrint and frmAudio have values in the listbox which the user can select and then the listbox control on frmMain gets updated with whatever values they select. I need to do some calcuations on the values that are entered on frmMain listbox. The problem is I can't seem to find the right event so I can calculate these values on the fly whenever the listbox has a item added or removed. foreach ( object o in lstProducts.Items) { if (o.ToString() == I Did It Your Way (Print) ) txtShipping.Text = works ; } I've tried the SelectedIndexChanged and SelectedValueChange and the form_Load and form_enter events with the above code none work. the selectedIndexChange requires me to click an item in the listbox. This is not what I want. I want it to automatically and on the fly do the calcuations (or in the above code display the text in the textbox.) Am I clear here? Advice/suggestions please.

Jan Montano · Answer

Hi Tim Welcome! =) Richard is right. Oddly enough I can't see any event pertaining to the listbox's add item. One workaround is building a custom control which inherits from ListBox class and putting an ItemAddedEvent in it. public partial class MyListBox : ListBox { public event EventHandler ItemAddedEvent; public MyListBox() { InitializeComponent(); if (ItemAddedEvent == null ) { ItemAddedEvent = new EventHandler (MyListBox_ItemAddedEvent); } } public void Add( string value) { this .Items.Add(value); ItemAddedEvent( this  new EventArgs ()); } void MyListBox_ItemAddedEvent( object sender EventArgs e) { } } To use: public partial class Form1 : Form { public Form1() { InitializeComponent(); myListBox.ItemAddedEvent += new EventHandler (myListBox_ItemAddedEvent); } private void button1_Click( object sender EventArgs e) { myListBox.Add( Jan ); // instead of calling myListBox.Items.Add(Jan); } private void Form1_Load( object sender EventArgs e) { } void myListBox_ItemAddedEvent( object sender EventArgs e) { MessageBox .Show( New item added ); } } Cheers Jan

Richard Blythe · Answer

If I understand you correctly you want an event to fire when an item is added/removed. You are correct in assuming that the listbox control has no event for that operation. However you can create your own custom event and fire it when you add/remove an item. Is what you need? If so I will show you how to accomplish this. Cheers! Richard