Not sure if there is a binding for the items count.
You can just check the list views items count whenever you make a change and disable or enable the button. That would be pretty easy.
You can however create your own listview with an ItemChanged event.
This will look like overkill and it is if your only going to use it one time. But If you start making custom controls and keep adding to them then the future will allow you to drag and drop with all kinds of additional functionality.
I was board and decided to write this. I do have a ListViewPlus like the class below that has ItemMouseClick, Radio and Checkboxes, and more.
Theres really nothing special about the following. It shadows the Items Property to return the custom ListViewItemCollection. The Custom ListViewItem Collection will raise an Event whenever items change.
All you have to do is create a class named ListViewPlus and copy and paste the code into it. Rebuild the solution and the control will be in the toolbox. Drag it to the form and it will be identical to the listview except you will have an additional ItemChanged event. Put your code for enabling and disabling the button in the ItemChange Event.
Like I said I wrote this because I was bored. Use it or not.
The Form
Public Class Form1
Private Sub ListViewPlus_ItemChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListViewPlus1.ItemChanged
Button1.Enabled = ListViewPlus1.Items.Count > 0
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
ListViewPlus1.Items.Add("List View Plus")
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
ListViewPlus1.Items.Clear()
End Sub
End ClassThe Extended ListView
Imports System.ComponentModel
Imports System.Windows.Forms.Design
Public Class ListViewPlus : Inherits ListView
Public Event ItemChanged(ByVal sender As Object, ByVal e As EventArgs)
Private ItemsWathced As ListViewPlusItemCollection
Sub New()
ItemsWathced = New ListViewPlusItemCollection(Me)
AddHandler ItemsWathced.ItemChanged, AddressOf ListViewItemCollectionChanged
End Sub
Private Sub ListViewPlus_HandleCreated(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.HandleCreated
RaiseEvent ItemChanged(Me, EventArgs.Empty)
End Sub
'Designer Serialization allows what you do on the designer to show up when
'you run the program. The editor is for when your on the designer and you
'look at the items property you will see (Collection) and will be an identical
'designer when adding items to it as when you would a regular list view
<DesignerSerializationVisibility(DesignerSerializationVisibility.Content), _
Editor(GetType(ListViewItemCollectionEditor), GetType(System.Drawing.Design.UITypeEditor))> _
Shadows ReadOnly Property Items() As ListView.ListViewItemCollection
Get
Return ItemsWathced
End Get
End Property
Private Sub ListViewItemCollectionChanged(ByVal sender As Object, ByVal e As EventArgs)
RaiseEvent ItemChanged(Me, EventArgs.Empty)
End Sub
#Region "Custom Item Collection"
'Inherits the ItemCollection and raises an event each time something changes
'with the items.
Public Class ListViewPlusItemCollection : Inherits System.Windows.Forms.ListView.ListViewItemCollection
Public Event ItemChanged(ByVal sender As Object, ByVal e As EventArgs)
Sub New(ByVal owner As System.Windows.Forms.ListView)
MyBase.New(owner)
End Sub
Public Overrides Function Add(ByVal text As String) As System.Windows.Forms.ListViewItem
Dim ListItem As ListViewItem = MyBase.Add(text)
RaiseEvent ItemChanged(Nothing, Nothing)
Return ListItem
End Function
Public Overrides Function Add(ByVal text As String, ByVal imageIndex As Integer) As System.Windows.Forms.ListViewItem
Dim ListItem As ListViewItem = MyBase.Add(text, imageIndex)
RaiseEvent ItemChanged(Nothing, Nothing)
Return ListItem
End Function
Public Overrides Function Add(ByVal text As String, ByVal imageKey As String) As System.Windows.Forms.ListViewItem
Dim ListItem As ListViewItem = MyBase.Add(text, imageKey)
RaiseEvent ItemChanged(Nothing, Nothing)
Return ListItem
End Function
Public Overrides Function Add(ByVal key As String, ByVal text As String, ByVal imageIndex As Integer) As System.Windows.Forms.ListViewItem
Dim ListItem As ListViewItem = MyBase.Add(key, text, imageIndex)
RaiseEvent ItemChanged(Nothing, Nothing)
Return ListItem
End Function
Public Overrides Function Add(ByVal key As String, ByVal text As String, ByVal imageKey As String) As System.Windows.Forms.ListViewItem
Dim ListItem As ListViewItem = MyBase.Add(key, text, imageKey)
RaiseEvent ItemChanged(Nothing, Nothing)
Return ListItem
End Function
Public Overrides Function Add(ByVal value As System.Windows.Forms.ListViewItem) As System.Windows.Forms.ListViewItem
Dim ListItem As ListViewItem = MyBase.Add(value)
RaiseEvent ItemChanged(Nothing, Nothing)
Return ListItem
End Function
Shadows Sub AddRange(ByVal items() As ListViewItem)
MyBase.AddRange(items)
RaiseEvent ItemChanged(Nothing, Nothing)
End Sub
Public Overrides Sub Clear()
MyBase.Clear()
RaiseEvent ItemChanged(Nothing, Nothing)
End Sub
Public Overrides Function Insert(ByVal index As Integer, ByVal key As String, ByVal text As String, ByVal imageIndex As Integer) As System.Windows.Forms.ListViewItem
Dim ListItem As ListViewItem = MyBase.Insert(index, key, text, imageIndex)
RaiseEvent ItemChanged(Nothing, Nothing)
Return ListItem
End Function
Public Overrides Function Insert(ByVal index As Integer, ByVal key As String, ByVal text As String, ByVal imageKey As String) As System.Windows.Forms.ListViewItem
Dim ListItem As ListViewItem = MyBase.Insert(index, key, text, imageKey)
RaiseEvent ItemChanged(Nothing, Nothing)
Return ListItem
End Function
Public Overrides Sub Remove(ByVal item As System.Windows.Forms.ListViewItem)
MyBase.Remove(item)
RaiseEvent ItemChanged(Nothing, Nothing)
End Sub
Public Overrides Sub RemoveAt(ByVal index As Integer)
MyBase.RemoveAt(index)
RaiseEvent ItemChanged(Nothing, Nothing)
End Sub
Public Overrides Sub RemoveByKey(ByVal key As String)
MyBase.RemoveByKey(key)
RaiseEvent ItemChanged(Nothing, Nothing)
End Sub
End Class
#End Region
#Region "Custom Item Collection Editor"
'For designer use when adding items.
Public Class ListViewItemCollectionEditor
Inherits System.ComponentModel.Design.CollectionEditor
Public Sub New(ByVal newType As Type)
MyBase.new(newType)
End Sub
Protected Overrides Function CanSelectMultipleInstances() As Boolean
Return False
End Function
Protected Overrides Function CreateCollectionItemType() As Type
Return GetType(ListViewItem)
End Function
End Class
#End Region
End Class
I should say if you used this you would want to add multiple items with the AddRange sub. This will now have an event raised everytime you add an item and would perform worse than the regular listview. AddRange is better anyways and would have no affect with performance of the new event.
And the ItemChanged Event would be more meaningfull if it was renamed to ItemsCountChanged.
