How do I recognize a mouse click on a line?

Question

I have a WPF application. There is a canvas. I draw line when user drag the mouse over the canvas (from mouse down to mouse up). I take initial point, when mouse is pressed down and final point, when user does mouse up. Then I calculate the distance and draw the line in simple mouse down, move and up events.

After drawing many lines on canvas, I click on any one of the line. I want to select the line and show the user that line is selected (like by changing the color of the line). So user can delete it.

Thanks.

Line class, just like the canvas has events like MouseDown and so forth. You could hook up event handlers as you create them and deal with selecting the line in the handler. — Bala R

loxxy loxxy · Accepted Answer · 2011-09-26T14:48:59

Here is a working example: (implementing what Bala suggested in his comment)

private void myCanvas_Loaded(object sender, RoutedEventArgs e)
        {
            Line line = new Line();

            line.MouseDown += new MouseButtonEventHandler(line_MouseDown);
            line.MouseUp   += new MouseButtonEventHandler(line_MouseUp);

            line.Stroke = Brushes.Black;
            line.StrokeThickness = 2;
            line.X1 = 30; line.X2 = 80;
            line.Y1 = 30; line.Y2 = 30;

            myCanvas.Children.Add(line);
        }

void line_MouseUp(object sender, MouseButtonEventArgs e)
        {
            // Change line colour back to normal 
            ((Line)sender).Stroke = Brushes.Black;
        }

void line_MouseDown(object sender, MouseButtonEventArgs e)
        {
            // Change line Colour to something
            ((Line)sender).Stroke = Brushes.Red;
        }

Considering that you already have the logic to add the lines into canvas,

Simply add the two event handlers (as above) for every line that you add.

How do I recognize a mouse click on a line?

3 Answers