虚线形状以意外的比例绘制

Question

I am using a control paint event to draw graphic objects in my application. The sizes of all the object is stored with size unit of millimeters and therefore i use 'millimeter' as PageUnit for the graphic object. For some reason when i draw a shape with a DashStyle other than solid, it gets drawn in a very unexpected scale.

In the code example below I expect to see both lines being drawn one on top of the other, but what i get is the red dashed line being drawn elsewhere in larger scale.

Any idea what I am missing?

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication6
{
    public partial class Form1 : Form
    {
        private Pen solidBlackPen = new Pen(Color.Black, 1);
        private Pen dashedRedPen = new Pen(Color.Red, 1) { 
                                          DashStyle = DashStyle.Dash 
                                       };

        private Point point1 = new Point(5, 5);
        private Point point2 = new Point(35, 5);

        public Form1()
        {
            InitializeComponent();

            this.BackColor = Color.White;
            this.Paint += new PaintEventHandler(Form1_Paint);
        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            e.Graphics.PageUnit = GraphicsUnit.Millimeter;

            e.Graphics.DrawLine(solidBlackPen, point1, point2);
            e.Graphics.DrawLine(dashedRedPen, point1, point2);
        }

    }
}

Since I am new i cant upload a screenshot.

Answer 1

After few tests this looks to me like some kind of bug that occures mybe only on specific Os/framework.

What managed to fix me this was adding the following line before drawing the shapes:

e.Graphics.ScaleTransform(1, 1);