hey. I'm trying to maintain an MVVM model, but am tripping up somewhere when trying to bind to a listbox. The first time I run the application, I set ItemCatalog
(ObservableCollection) to be a certain ObservableCollection list. The listbox is empty, but if I try again it works. However, there is a lag between the datasource and the displayed data. For example,
I load the app -> set source to X
-> Listbox is empty
I now set source to Y
-> Listbox displays X
I set source to Z
-> Listbox displays Y
etc..
This, to me, implies the binding is working but I can't figure out why it's lagging by one.
My XAML looks like this:
<ListBox ItemsSource="{Binding ItemCatalog}">
<DataTemplate>
<StackPanel Margin="0,0,0,17" Width="432">
<TextBlock Text="{Binding Ref}" TextWrapping="Wrap" Foreground="Black" />
<TextBlock Text="{Binding ItemName}" TextWrapping="Wrap" Margin="12,-6,12,0" Foreground="Black" />
</StackPanel>
</DataTemplate>
</ListBox>
In the ViewModel, the value of ItemCatalog
is based on whichever button the user pressed (X
,Y
,Z
), which are all stored in a static variable. Is there a reason there's a delay, or a way to force it to rebind to the latest ItemCatalog
value?
If I remove the binding from the XAML and set the listbox source straight from the code-behind, it works perfectly. However, I want to try and maintain the XAML coding. I'm new to MVVM so I might be doing this the wrong way round. thanks
EDIT - extra code
The code is changed in the OnNavigatedTo method
protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
if (NavigationContext.QueryString["Category"].ToString() == "House")
{
_categoryType = Models.House;
}
if (NavigationContext.QueryString["Category"].ToString() == "Car")
{
_categoryType = Models.Car;
}
MyViewModel.LoadNewData(_categoryType);
base.OnNavigatedTo(e);
}
LoadNewData
method just sets the static variable based on the parameter passed.
ItemCatalog = App.CarCatalog;
Essentially, I need to rebind after the page has loaded, via XAML.