Sometimes cannot select item in Listbox c# - wpf

Question

In my xaml I bind a ObservableCollection<City> Cities to it
and the SelectedItem is SelectedCity
and sometimes when the mouse is over a item, I cannot select it
My ListBox looks like this:
<ListBox ItemsSource="{Binding Model.Cities}" SelectedItem="{Binding Model.SelectedCity}" HorizontalAlignment="Left" Height="468" Margin="10,136,0,0" VerticalAlignment="Top" Width="877">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Margin="0,2">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="100" />
<ColumnDefinition Width="150" />
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="0" Text="{Binding Name}" />
<TextBlock Grid.Column="1" Text="{Binding Plz}" />
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
and in My Model the code looks like this:
class CitiesModel: MyObservableCollection<City>
{
public ObservableCollection<City> Cities
{
get
{
return _cities;
}
}
private ObservableCollection<City> _cities;
private City _selectedCity;
public City SelectedCity
{
get
{
return _selectedCity;
}
set
{
_selectedCity = value;
RaisePropertyChanged("SelectedCity");
}
}
Can someone explain, why i sometimes cannot select an item?

Answer 1

You mean once you select one, you cannot select a different one.
Your problem is that if you have in the setter.
Remove it.
if(_selectedCity != value)
{
City is an object.
If you compare an object to another then unless you have provided an Equals method, they will be equal if of the same type.
Hence, once you select a City then any other City is equal.