C# Question

How to draw a dashed line over an object?

I am drawing a line on a control on my Windows form like this:

// Get Graphics object from chart
Graphics graph = e.ChartGraphics.Graphics;

PointF point1 = PointF.Empty;
PointF point2 = PointF.Empty;

// Set Maximum and minimum points
point1.X = -110;
point1.Y = -110;
point2.X = 122;
point2.Y = 122;

// Convert relative coordinates to absolute coordinates.
point1 = e.ChartGraphics.GetAbsolutePoint(point1);
point2 = e.ChartGraphics.GetAbsolutePoint(point2);

// Draw connection line
graph.DrawLine(new Pen(Color.Yellow, 3), point1, point2);


I would like to know if it is possible to draw a dashed (dotted) line instead of a regular solid line?

Answer

It's pretty simple once you figure out the formatting that defines the dashes:

float[] dashValues = { 5, 2, 15, 4 };
Pen blackPen = new Pen(Color.Black, 5);
blackPen.DashPattern = dashValues;
e.Graphics.DrawLine(blackPen, new Point(5, 5), new Point(405, 5));

The numbers in the float array represent dash lengths of different colors. So for a simple dash of 2 pixels on (black) and two off each your aray would look like: {2,2} The pattern then repeats. If you wanted 5-wide dashes with a space of 2 pixels you would use {5,2}

In your code it would look like:

// Get Graphics object from chart
Graphics graph = e.ChartGraphics.Graphics;

PointF point1 = PointF.Empty;
PointF point2 = PointF.Empty;

// Set Maximum and minimum points
point1.X = -110;
point1.Y = -110;
point2.X = 122;
point2.Y = 122;

// Convert relative coordinates to absolute coordinates.
point1 = e.ChartGraphics.GetAbsolutePoint(point1);
point2 = e.ChartGraphics.GetAbsolutePoint(point2);

// Draw (dashed) connection line
float[] dashValues = { 4, 2 };
Pen dashPen= new Pen(Color.Yellow, 3);
dashPen.DashPattern = dashValues;
graph.DrawLine(dashPen, point1, point2);
Comments