Refreshing OxyPlot Chart

Question

I'm working on a WPF app. This app uses the OxyPlot chart control. I am letting the user perform a calculation. The user can view the result in both grid and chart form. In an attempt to do this, I have the following:

home.xaml

<DataGrid x:Name="resultDataGrid" ItemsSource="{Binding Items}">
  <DataGrid.Columns>
    <DataGridTextColumn Header="#" Binding="{Binding Number}" />
    <DataGridTextColumn Header="Description" Binding="{Binding Description}" />
  </DataGrid.Columns>
</DataGrid>

<oxy:Plot x:Name="resultGraph" Background="Transparent" Height="400" HorizontalContentAlignment="Stretch" VerticalAlignment="Stretch" Visibility="Collapsed">
  <oxy:Plot.Series>
    <oxy:LineSeries ItemsSource="{Binding Points}" MarkerType="Circle"  Title="Result" />
  </oxy:Plot.Series>
</oxy:Plot>

<StackPanel Orientation="Horizontal">
  <Button x:Name="executeButton" Click="executeButton_Click" />
  <Button x:Name="viewData" Click="viewData_Click" />
  <Button x:Name="viewChart" Click="viewChart_Click" />
</StackPanel>

home.xaml.cs

public partial class Home: Page
{
  private MyViewModel viewModel = null;
  public Home()
  {
    InitializeComponent();

    viewModel = new MyViewModel();
    this.DataContext = viewModel;
  }

  private void executeButton_Click(object sender, RoutedEventArgs e) {
    viewModel.Execute();
  }

  private void viewData_Click(object sender, RoutedEventArgs e) 
  {
    resultDataGrid.Visibility = System.Windows.Visibility.Visible;
    resultGraph.Visibility = System.Windows.Visibility.Collapsed;
  }

  private void viewChart_Click(object sender, RoutedEventArgs e)
  {
    resultDataGrid.Visibility = System.Windows.Visibility.Collapsed;
    resultGraph.Visibility = System.Windows.Visibility.Visible;
  }
}

MyViewModel.cs

public class MyViewModel : INotifyPropertyChanged
{
  public Dictionary<int, string> Items{ get; set; }
  public IList<DataPoint> Points{ get; set; }

  public void Execute() 
  {
    this.Items = new Dictionary<int, string>();
    this.Points = new List<DataPoint>();

    var randomNumber = GetRandomNumber();
    for (var i=0; i<10; i++) 
    {
      this.Items.Add((i+1), "Item #" + i);

      var dataPoint = new DataPoint(i, (randomNumber*i));
      this.Points.Add(dataPoint);
    }

    NotifyPropertyChanged("Items");
    NotifyPropertyChanged("Points");
  }
}

My problem is, when a user clicks the "Execute" button, the data gets refreshed for in the DataGrid, which is what I am expecting. However, the chart only gets refreshed if the chart is first visible. In other words, if I click "execute" when the DataGrid is visible, the plot points in the chart become stale. But, If I have the resultGraph visible and I click "Execute" the points get refreshed as expected. I do not understand what I'm doing wrong. Any help is appreciated.

Answer 1

in your ViewModel create

private int _invalidateFlag = 0;
public int InvalidateFlag
{
   get {return _invalidateFlag;}
   set
   {
      _invalidateFlag = value;
      NotifyPropertyChanged();
   }
}

//and to the end of Execute() add

InvalidateFlag++;

also don't forget to bind the InvalidateFlag

<oxy:Plot x:Name="resultGraph" InvalidateFlag="{Binding InvalidateFlag}" Background="Transparent" Height="400" HorizontalContentAlignment="Stretch" VerticalAlignment="Stretch" Visibility="Collapsed">

this should do the trick