README.md

How to Select Multiple Scatter Data Points with Mouse Drag

The WPF Chart allows you to select multiple scatter data points using the canvas and mouse drag.

Here are the steps to follow:

Step 1: Create a scatter chart within a grid layout using this documentation

Step 2: Initialize the canvas with mouse interaction events.

Step 3: Implement the mouse interaction events to select the desired data points using the mouse drag.

C#

    public partial class MainWindow : Window
    {
        #region Fields

        private Point startPoint;
        private Rectangle? currentRectangle;
        private Rect currentRect;

        #endregion

        #region Constructor

        public MainWindow()
        {
            InitializeComponent();
        }

        #endregion

        #region Methods

        private void OnMouseMove(object sender, MouseEventArgs e)
        {
            if (e.LeftButton == MouseButtonState.Pressed && currentRectangle != null)
            {
                // Update the size of the rectangle as the mouse is dragged.
                double width = e.GetPosition(drawingCanvas).X - startPoint.X;
                double height = e.GetPosition(drawingCanvas).Y - startPoint.Y;
                if (width > 0 && height > 0)
                {
                    currentRect = new Rect(startPoint.X, startPoint.Y, width, height);
                    currentRectangle.Width = width;
                    currentRectangle.Height = height;
                }
            }
        }

        private void OnMouseDown(object sender, MouseButtonEventArgs e)
        {
            startPoint = e.GetPosition(drawingCanvas);

            // Create a new rectangle.
            currentRectangle = new Rectangle
            {
                Stroke = Brushes.Black,
                StrokeThickness = 1,
                Fill = Brushes.Transparent
            };

            // Add the rectangle to the canvas.
            drawingCanvas.Children.Add(currentRectangle);

            // Set the initial position of the rectangle.
            Canvas.SetLeft(currentRectangle, startPoint.X);
            Canvas.SetTop(currentRectangle, startPoint.Y);
        }

        private void OnMouseUp(object sender, MouseButtonEventArgs e)
        {
            viewModel.SelectedDataPoints = series.GetDataPoints(currentRect);
            currentRectangle = null;
            currentRect = Rect.Empty;
            drawingCanvas.Children.Clear();
        } 

        #endregion
    } 

The following demo visualizes how to select multiple scatter data points using mouse drag, which shows the respective values in a list view.

Troubleshooting

Path too long exception

If you are facing a path too long exception when building this example project, close Visual Studio and rename the repository to short and build the project.

For more details, refer to the KB on how to select multiple scatter data points using the mouse drag.