WPF, Prevent selected item change in condition - wpf

Question

I have a listview like:
<ListView Name="ListViewItems" Grid.Row="2" Foreground="White" ItemsSource="{Binding Items}"
SelectedItem="{Binding CurrentSelectedItem ,Mode=TwoWay}"
ScrollViewer.HorizontalScrollBarVisibility="Disabled" SelectionMode="Single"
HorizontalContentAlignment="Stretch"
ScrollViewer.VerticalScrollBarVisibility="Auto"
VerticalAlignment="Stretch" BorderThickness="0" >
<ListView.ItemTemplate>
<DataTemplate >
<Grid >
<Grid.RowDefinitions>
<RowDefinition Height="25"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.5*"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Label Grid.Column="0" Width="0" Visibility="Collapsed" Content="{Binding Id}"/>
<Label Grid.Column="0" Content="{Binding Name}" HorizontalContentAlignment="Left" Foreground="White" FontWeight="Bold" Background="Transparent"/>
<Label Grid.Column="1" Content="{Binding Provider}" HorizontalContentAlignment="Left" Foreground="White" Background="Transparent"/>
<Label Grid.Column="0" Grid.ColumnSpan="2" Background="Transparent"/>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
As it seems when i change the selected item (by clicking on another listview item) the set of CurrentSelectedItem will be called.
private MyObject _currentSelectedItem;
public MyObject CurrentSelectedItem
{
get => _currentSelectedItem;
set
{
if (Condition)
{
// here i want to have previous item seleced
// Currently i do nothing here
}
else
{
_currentSelectedItem = value;
}
}
}
When Condition is true if I do nothing the CurrentSelectedItem will have previous value which is what I want, BUT in the UI the selected item (highlighted item) is the one I selected recently.
What I want is to prevent such behavior in UI. I mean CurrentSelectedItem has not changed bu UI it changed.
Any solution to prevent such behavior? thanks in advance.
Solution:
As #Zeb-ur-Rehman we should save the previous state in _previousSelectedItem. but in the else statement i don't assign value to _currentSelectedItem as a result when I do _currentSelectedItem = _previousSelectedItem both current and previous mentioning the same object. and therefor OnPropertyChanged will not update the binded view.
By the way, the only way I could somehow manage this scenario is to save _currentSelectedMap in the previous and update UI by _currentSelectedMap = null.then after a small delay (it should be a delay) update UI by saved value like this:
if (Condition)
{
_previousSelectedItem = _currentSelectedItem;
_currentSelectedItem = null;
NotifyOfPropertyChange(()=> CurrentSelectedItem);
Task.Delay(100).ContinueWith(x =>
{
Application.Current.Dispatcher.Invoke(() =>
{
_currentSelectedItem = _previousSelectedItem;
NotifyOfPropertyChange(()=> CurrentSelectedItem);
});
});
}
else
{
_currentSelectedItem = value;
}

Answer 1

Here is what you need to do in your property setter.
private MyObject _previousSelectedItem;
private MyObject _currentSelectedItem;
public MyObject CurrentSelectedItem
{
get => _currentSelectedItem;
set
{
if (Condition)
{
_previousSelectedItem = _currentSelectedItem;
_currentSelectedItem = value;
}
else
{
_currentSelectedItem = _previousSelectedItem;
}
NotifyOfPropertyChange(()=> CurrentSelectedItem);
}
}
You need to keep track of previous value which you can capture when changing the currentSelectedItem. Next time if the condition is not true then just assign your currentSelecteditem the previous value.
Hope it will work for you.
Edit:
I haven't mentioned that you need to NotifyOfPropertyChange(()=> CurrentSelectedItem); becuase i thought it's too obvious. Your code should work this way as well. Insead of changing value in Dispatcher, as the value is already 2 way bind to control. This is the power of WPF binding.