Binding Checkbox to a Shared Property in a custom class - vb.net

Question

So this should be simple I guess, but I have never done this.
Got a form on which I have a checkbox. I want this check box to be directly linked to a custom class's Boolean property, but somehow this does not work.
Public Class someClass
Private Shared _Filter_Neighbor_6X1 As Boolean = True
Shared Property Filter_Neighbor_6X1() As Boolean
Get
Return _Filter_Neighbor_6X1
End Get
Set(ByVal Value As Boolean)
_Filter_Neighbor_6X1 = Value
End Set
End Property
End Class
Public Class GameGUI
Private Sub GameGUI_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
chk_FilterAll.DataBindings.Add("Checked", someClass, "Filter_Neighbor_6X1")
end sub
End Class
The above does not work. It complains the "someClass" is a class.
I also tried:
chk_FilterAll.DataBindings.Add( _
New Binding("Checked", someClass, "Filter_Neighbor_6X1", _
False, DataSourceUpdateMode.OnPropertyChanged, False))
which hangs the app on start.
any help is appreciated.
Thanks!

Answer 1

You can't bind to a Shared property. You need to remove the Shared modifier from the property, create an instance of the class, and use that instance for the data binding. Your class would look something like this:
Public Class someClass
Private _Filter_Neighbor_6X1 As Boolean = True
Public Property Filter_Neighbor_6X1() As Boolean
Get
Return _Filter_Neighbor_6X1
End Get
Set(ByVal Value As Boolean)
_Filter_Neighbor_6X1 = Value
End Set
End Property
End Class
Then you can do something like:
Dim instanceOfSomeClass As New someClass()
chk_FilterAll.DataBindings.Add("Checked", instanceOfSomeClass, "Filter_Neighbor_6X1")
Note that if you don't have extra logic under the Get or Set of the property, you can get rid of the backing field and convert it to an Auto-Implemented (shorthand) property:*
Public Property Filter_Neighbor_6X1 As Boolean = true
Moreover, if you don't want to create an instance of the class each time, you can make it a Singleton:
Public Class someClass
Private Shared _instance As someClass
Private Sub New()
End Sub
Public Shared ReadOnly Property Instance As someClass
Get
If _instance Is Nothing Then _instance = New someClass()
Return _instance
End Get
End Property
Public Property Filter_Neighbor_6X1 As Boolean = True
End Class
Then, you can use it directly like this:
chk_FilterAll.DataBindings.Add("Checked", someClass.Instance, "Filter_Neighbor_6X1")
* You probably do need extra logic in this particular case in order to notify the change of the property so that the control can reflect that change. Check the other answer for more info.

Answer 2

If you don't want to get rid of the Shared modifier, you can add a read-only property which returns the value of the Shared one:
Public Class someClass
' ...
' ...
' TODO: Remember to use a different name.
Public ReadOnly Property MyNonSharedProperty As Boolean
Get
Return Filter_Neighbor_6X1
End Get
End Property
End Class
Then you can use it like this:
Dim instanceOfSomeClass As New someClass()
chk_FilterAll.DataBindings.Add("Checked", instanceOfSomeClass, "MyNonSharedProperty")
Or with the Singleton approach (check the other answer for details):
chk_FilterAll.DataBindings.Add("Checked", someClass.Instance, "MyNonSharedProperty")
However, please note that if you're implementing the INotifyPropertyChanged interface in your class*, you'll need to notify the change of the read-only property as well as the Shared one when the latter gets changed.
Full implementation:
Public Class someClass
Implements INotifyPropertyChanged
' ##################################
' Optional: Add Singleton logic here
' ##################################
Private _Filter_Neighbor_6X1 As Boolean = True
Public Property Filter_Neighbor_6X1() As Boolean
Get
Return _Filter_Neighbor_6X1
End Get
Set(ByVal Value As Boolean)
_Filter_Neighbor_6X1 = Value
NotifyPropertyChanged()
' TODO: Remember to change the name of the property.
NotifyPropertyChanged("MyNonSharedProperty")
End Set
End Property
' TODO: Remember to use a different name.
Public ReadOnly Property MyNonSharedProperty As Boolean
Get
Return Filter_Neighbor_6X1
End Get
End Property
Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
Private Sub NotifyPropertyChanged(<CallerMemberName()> Optional ByVal propertyName As String = Nothing)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub
End Class
* Which is something you should do when using the class as a DataBinding source.