code for 'Data'

     public ObservableCollection<Graph> Data { get; set; }

Graph object:

      {public class Graph : INotifyPropertyChanged
{
private TimeSpan time;
private double units;

public event PropertyChangedEventHandler PropertyChanged;

public TimeSpan Time
{
    get { return time; }

    set
    {
        time = value;
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Time"));
    }
}

public double Units
{
    get { return units; }

    set
    {
        units = value;
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Time"));
    }
}
}

'Data' is a list of 'Graph' objects and I need to display the value of the 'Unit' in the last Graph object of the list, 'Data'. How can I do it in xaml with data binding? This is what I tried and it doesn't work:

        <Label Grid.Row="0" Grid.Column="2" Text="{Binding Data[Data.Count-1].Units}"/>

Really appreciate the help! Thanks a lot!

CodePudding user response：

you can use a converter for this.

CodePudding user response：

You could try the code below.

ViewModel:

  public class GraphViewModel
{
    public ObservableCollection<Graph> Data { get; set; }
    public GraphViewModel()
    {
        Data = new ObservableCollection<Graph>()
        {
            new Graph(){  Time = new TimeSpan(0,0,0), Units=1 },
            new Graph(){  Time = new TimeSpan(0,0,0), Units=2 },
            new Graph(){  Time = new TimeSpan(0,0,0), Units=3 },
            new Graph(){  Time = new TimeSpan(0,0,0), Units=4 },
            new Graph(){  Time = new TimeSpan(0,0,0), Units=5 },

        };
    }

}

Xaml:

<ContentPage.Content>

    <Label  Text="{Binding .}"/>

</ContentPage.Content>

Code behind:

 public partial class Page4 : ContentPage
{
    GraphViewModel viewModel;
    public Page4()
    {
        InitializeComponent();
        viewModel = new GraphViewModel();
       
        this.BindingContext = viewModel.Data[viewModel.Data.Count - 1].Units;
    }
}