How to clear WPF ItemList after binding the itemsource? - wpf

Question

I have a list:
private ObservableCollection<SensorListViewItemModel> sensorList = new ObservableCollection<SensorListViewItemModel>();
In which my Model is this:
public class SensorListViewItemModel
{
/// <summary>
/// Gets or sets the internal Id.
/// </summary>
public Guid InternalId { get; set; } = Guid.NewGuid();
/// <summary>
/// Gets or sets the name.
/// </summary>
public string Name { get; set; }
/// <summary>
/// Get or sets the point.
/// </summary>
public System.Drawing.PointF PointOnImage { get; set; }
/// <summary>
/// Gets or sets the number of this sensor.
/// </summary>
public int Number { get; set; }
/// <summary>
/// Gets or sets the fill color.
/// </summary>
public Color Color { get; set; } = Colors.Black;
/// <summary>
/// Covnerter for Brush and MVVM Data Binding in the ListView
/// </summary>
public Brush ColorAsBrush
{
get
{
return new SolidColorBrush(Color);
}
}
}
Now I bind this in my WindowLoaded Event of my WPF window to my ListView:
this.SensorListView.ItemsSource = this.sensorList;
Now I add some items which works fine:
this.sensorList = new ObservableCollection<SensorListViewItemModel>();
for (int i = 1; i <= 5; i++)
{
this.sensorList.Add(new SensorListViewItemModel()
{
Number = i,
Name = "Sensor " + i,
Color = ColorHelper.FromStringAsMediaColor(this.userSettings.DataSerieColors[i - 1])
});
}
Now the item list shows 5 items - okay.
Now I want to clear the iteams:
this.sensorList.Clear();
or
this.sensorList = new ObservableCollection<SensorListViewItemModel>();
but both doesn't work

Answer 1

The whole purpose of ObservableCollection is that you should only create it once, and then just modify the existing collection.
As Clemens has pointed out in the comments, you're not doing data-binding - you need a public property on your ViewModel for that.
So your ViewModel code should be something like
public class SensorListViewModel
{
private readonly ObservableCollection<SensorListViewItemModel> _sensorList = new ObservableCollection<SensorListViewItemModel>();
public IEnumerable<SensorListViewItemModel> SensorList => _sensorList;
private void AddSensorItems(IEnumerable<SensorListViewItemModel> items, bool clearExistingItems)
{
if (clearExistingItems)
_sensorList.Clear();
foreach(var item in items)
_sensorList.Add(item);
}
Note that you don't have to declare the SensorList property as ObservableCollection - the binding will take care of that.
Then in your View, set its DataContext to an instance of SensorListViewModel and bind the ItemsSource property of the ListView to the SensorList property.