I am rather new to the WPF setup and I am running into an issue where as far as I can see I have set it up correctly to have my combobox bound to a observable collection of object.

The Combobox will update when I add or delete items. If I make a change the items in the drop down will not show any differently but if I select one that was edited it will now show the new information but only when selected. 

I have set up the object class to use INotifyPropertyChanged correctly I think but it does not seem to be functioning. Going to attach the code below so that you can easily see exactly what I am trying to describe. 

What I am trying to do it allow a user to push a button and have the text inside a combobox update to show the new text. 

```
Imports System.ComponentModel

Public Class Window2
    Public _names As New System.Collections.ObjectModel.ObservableCollection(Of TestClass)

    Public Sub BaseLoading() Handles MyBase.Loaded

        Dim AddNewItem As New TestClass
        AddNewItem.groupName = "Item " + (_names.Count + 1).ToString
        _names.Add(AddNewItem)

        cbo_Names.SetBinding(ItemsControl.ItemsSourceProperty, New Binding With {.Source = _names})
    End Sub

    Private Sub button_PreviewMouseDown(sender As Object, e As MouseButtonEventArgs)
        Dim AddNewItem As New TestClass
        AddNewItem.groupName = "Item " + (_names.Count + 1).ToString
        _names.Add(AddNewItem)
        _names(0).groupName = ("Value Changed")
    End Sub
End Class

Public Class TestClasss
    Implements INotifyPropertyChanged

    Public _groupName As String = ""

    Public Property groupName As String
        Get
            Return _groupName.ToString
        End Get
        Set(value As String)
            _groupName = value
            onPropertyChanged(New PropertyChangedEventArgs(_groupName))
        End Set
    End Property

    Public Event PropertyChagned(ByVal sender As Object, ByVal e As PropertyChangedEventArgs) Implements INotifyPropertyChanged.PropertyChanged
    Public Sub onPropertyChanged(ByVal e As PropertyChangedEventArgs)
        RaiseEvent PropertyChagned(Me, e)
    End Sub
End Class

```

XAML 

```
<Window x:Class="Window2"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <StackPanel>
        <Button x:Name="button" Content="Button" PreviewMouseDown="button_PreviewMouseDown"/>
        <ComboBox x:Name="cbo_Names"  Margin="30,5,30,5" IsEditable="False" ItemsSource="{Binding _names, NotifyOnSourceUpdated=True,Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" DisplayMemberPath="groupName"     SelectedItem="{Binding _names, NotifyOnSourceUpdated=True,Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" />
    </StackPanel>
</Window>

```

I would appreciate any help locating what I am missing.