Question

I ‘m creating a Line chart using WPFToolKit.

The chart comes up fine but i want to change the Maximum property of the Y Axis upon button click of a modal window after loading the chart for the first time. And the chart should be refreshed with the updated Y Axis Max value

Below line shows how Chart is defined in xaml.

<DVC:Chart Canvas.Top="80" Canvas.Left="10" Name="mcChart" VerticalAlignment="Stretch"/>

I’m calling below code in windows.xaml.cs constructor and it is setting Y-Axis Max to 200

mcChart.Axes.Add(new LinearAxis()
        {
            Minimum = 0,
            Maximum = YMax > 0 ? YMax : 200,
            Orientation = AxisOrientation.Y,
            ShowGridLines = true,               
        });

        mcChart.UpdateLayout(); 

How can i change the Y-Axis Max value from a modal window’s button click event and refresh chart to display with new YMax.

I’m not sure if i have to do something with RegisteredListeners.
I’m new to WPF and any help is appreciated!

Please note that i’m looking to achieve this from the C# code behind and not in xaml.

Thanks,
Sujay

Answer 1

If you have access to the chart, you can find the neccessary axis and change the Maximum property without updating layout. Here is an example with a linear Y axis:

var yAxis = this.mcChart.ActualAxes.OfType<LinearAxis>().FirstOrDefault(ax => ax.Orientation == AxisOrientation.Y);
if (yAxis != null)
    yAxis.Maximum = 300;

The complete version of this example:

MainWindow.xaml

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="20"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <Button Content="Set max value = 300" HorizontalAlignment="Center" Click="Button_Click"/>
    <charting:Chart Grid.Row="1" x:Name="mcChart">
        <charting:Chart.Series>
            <charting:LineSeries ItemsSource="{Binding LineItems}" IndependentValuePath="Date" DependentValuePath="Value"/>
        </charting:Chart.Series>
    </charting:Chart>
</Grid>

MainWindow.xaml.cs

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        //Add a linear Y axis
        int YMax = 150;
        mcChart.Axes.Add(new LinearAxis()
        {
            Minimum = 0,
            Maximum = YMax > 0 ? YMax : 200,
            Orientation = AxisOrientation.Y,
            ShowGridLines = true,
        });

        //Create and set a view model
        var items = Enumerable.Range(0, 50).Select(i => new ChartItemModel { Date = new DateTime(2010, 1, 1).AddDays(i), Value = 30 + i }).ToList();
        this.DataContext = new MainViewModel { LineItems = items };
    }

    //Set Maximum=300
    private void Button_Click(object sender, RoutedEventArgs e)
    {
        var yAxis = this.mcChart.ActualAxes.OfType<LinearAxis>().FirstOrDefault(ax => ax.Orientation == AxisOrientation.Y);
        if (yAxis != null)
            yAxis.Maximum = 300;
    }
}

public class MainViewModel
{
    public List<ChartItemModel> LineItems { get; set; }
}

public class ChartItemModel
{
    public DateTime Date { get; set; }
    public double Value { get; set; }
}