Greying out or preventing listview item selection?

Here is a very simple solution using the SelectedIndexChanged event handler for the ListBox control.

I'm checking to make sure the index is greater than -1 as that is an invalid index (-1 means nothing is selected). You can modify this as needed but as it stands the snippet makes it so any listbox item clicked on with the value "I can't be selected" will then clear all items selected. Use this event handler as you wish.
Hint: Change the backcolor of items :p

Private Sub ListBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ListBox1.SelectedIndexChanged
    If ListBox1.SelectedIndex > -1 And
        ListBox1.Items(ListBox1.SelectedIndex) = "I can't be selected" Then
        ListBox1.ClearSelected()
    End If
End Sub

Here is another example to disable a listview item using combination of checkbox and ItemCheck Event. There also explanation on how to grey out the item.

c# - How do you disable an item in listview control in .net 3.5 - Stack Overflow[^]

Very late, but it could be usefull for others :)

Using MVVM, you should bind the IsHitTestVisible property of the ListViewItem to a property of your business object.

An example:
We have a list of clsMyClass object, used as ItemsSource for our list.
The class clsMyClass has a boolean property IsSelectable
Our XAML shoul be like this:

<listview itemssource="{Binding MyList}" selectionmode="Single"> <listview.itemcontainerstyle>
<Setter Property="IsHitTestVisible" Value="{Binding IsSelectable}"></setter>

In this way the items with IsSelectable=False will be not visible to the hit test, which means that the ListView will not intercept the mouse events and will not select it once clicked.

Note: this solution is not perfect in a multi-selection environment, because all items can be selected anyway using keybord shortcuts like Ctrl+A or Shift during selection.