c# - Change background color of ListView row programmatically (wpf)

Question

I have a class that populates a ListView by passing a list of objects. The class uses reflection to see the properties of each object in order to generate the ListView. How could I change the background color of a row in the ListView.

This page does exactly what I am looking for. The only problem is that my ListView is bound to the list of objects. In other words each item of the ListView is an object that is bound instead of a ListViewItem. I am assuming that is the reason why I cannot cast some item in the ListView to a ListViewItem. For example when I do this:

ListViewItem someItem = (ListViewItem)listView1.Items[0];

I get an InvalidcastException because if I where to physically add the objects to the ListView like:

listview.items.add(someObject) then this will work, but because I am binding the list to the ListView that line does not work. I think that is the reason why I am not able to cast. The reason why I want to cast it is becasue a ListViewItem has a Background property.

EDIT

I am able to do that with the first 12 objects I have tried the folowing:

for (int i = 0; i < listView1.Items.Count; i++)
{
    var lvitem = listView1.ItemContainerGenerator.ContainerFromIndex(i) as ListViewItem;
    lvitem.Foreground = Brushes.Green;                
}

and I get this error:

and I also have tried this:

foreach (Tiro t in listView1.Items)
{
    var lvitem = listView1.ItemContainerGenerator.ContainerFromItem(t) as ListViewItem;
    if (t.numero == 0 || t.numero == 37)
    {
        //lvitem.Background = Brushes.Green;
        lvitem.Foreground = Brushes.Green;
    }
    else if (t.numero % 2 == 0)
    {
        //lvitem.Background = Brushes.Red;
        lvitem.Foreground = Brushes.Red;
    }
    else
    {
        //lvitem.Background = Brushes.Gray;
        lvitem.Foreground = Brushes.Black;
    }

}

and I get the same error:

I don't understand why lvitem is null after the 12 iteration?

It only works with the items that are being displayed....

Answer 1

You need to introduce ViewModels instead of shredding the WPF UI. e.g. I could create one as follows

public class ItemVM : INotifyPropertyChanged // if you want runtime changes to be reflected in the UI
{
  public string Text {... raise property change in setter }
  public Color BackgroundColor {... ditto... }
}

Next create a list of such objects as a property in your DataContext so that your ListView can bind to it.

// e.g. MainWindow
    public IEnumerable<ItemVM> Items { get; set; }

Now all you need to do is bind your ListView to this collection and wire up the DataContext of the UI properly

       <ListView x:Name="MyListView" ItemsSource="{Binding Items}" HorizontalContentAlignment="Stretch">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Text}">
                    <TextBlock.Background>
                        <SolidColorBrush Color="{Binding BackgroundColor}"/>
                    </TextBlock.Background>
                    </TextBlock>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
        <Button Click="Button_Click" Content="Go PaleGreen"/>

Now changing the background color is easy. Just set the property of the corresponding ItemVM object to the Color you want. e.g. to set all items to go PaleGreen

private void Button_Click(object sender, RoutedEventArgs e)
    {
        foreach (var item in Items)
            item.BackgroundColor = Colors.PaleGreen;
    }