Winforms – n event that triggers if the number of ListViewItems in a ListView changes? (Windows Forms)

eventslistviewwinforms

I'd like to enable/disable some other controls based on how many items are in my ListView control. I can't find any event that would do this, either on the ListView itself or on the ListViewItemCollection. Maybe there's a way to generically watch any collection in C# for changes?

I'd be happy with other events too, even ones that sometimes fire when the items don't change, but for example the ControlAdded and Layout events didn't work :(.

Best Solution

@Domenic

Not too sure, Never quite got that far in the thought process.

Another solution might be to extend ListView, and when adding and removing stuff, instead of calling .items.add, and items.remove, you call your other functions. It would still be possible to add and remove without events being raised, but with a little code review to make sure .items.add and .items.remove weren't called directly, it could work out quite well. Here's a little example. I only showed 1 Add function, but there are 6 you would have to implement, if you wanted to have use of all the available add functions. There's also .AddRange, and .Clear that you might want to take a look at.

Public Class MonitoredListView
    Inherits ListView

    Public Event ItemAdded()
    Public Event ItemRemoved()

    Public Sub New()
        MyBase.New()
    End Sub

    Public Function AddItem(ByVal Text As String) As ListViewItem
        RaiseEvent ItemAdded()

        MyBase.Items.Add(Text)
    End Function

    Public Sub RemoveItem(ByVal Item As ListViewItem)
        RaiseEvent ItemRemoved()

        MyBase.Items.Remove(Item)
    End Sub

End Class

Related Solutions

C# – user control in a selectable list – best way to do it

What you may want to try is have two user controls. One control which you seem to already have, which is the icon and the labels. This will be an internal control that you can't instantiate outside of your assembly. The second user control, will just be a container of sorts (you can do this either by actually using a user control, or inheriting from a panel or whatever, doesn't matter). This will just serve as a collection of the individual items, and it will manage the selecting and unselecting of the items.

Basically, each user control will raise the click event, which your container user control will hook up to. It will then know which to select, and which to unselect.

Hope that makes sense!

R – .NET ListView: event after changing selection

Here's my solution in VB.NET, using the technique described in ObjectListView as suggested by Grammarian:

Private idleHandlerSet As Boolean = False

Private Sub listview1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles listview1.SelectedIndexChanged
    '' may fire more than once
    If Not idleHandlerSet Then
        idleHandlerSet = True
        AddHandler Application.Idle, New EventHandler(AddressOf listview1_SelectionChanged)
    End If
End Sub

Private Sub listview1_SelectionChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
    '' will only fire once
    idleHandlerSet = False
    RemoveHandler Application.Idle, New EventHandler(AddressOf listview1_SelectionChanged)
    DoSearch()
End Sub

Best Solution

Related Solutions

C# – user control in a selectable list – best way to do it

R – .NET ListView: event after changing selection

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