[C#] 繪製格線

FB 論壇上問題，之前作自訂控件時，也常常遇上繪製線條效果不如預期，這算是數學邏輯練習題，大神很數學的回答

寬度要 10n + 1 才能畫 n + 1 條線

C# WinForm Code

• PicutreBox：用來繪製格線
• ComboBox：設定 PictureBox 長寬

namespace GraphicsNETSample
{
    public partial class frmGridLine : Form
    {
        private int _cellLength { get; init; } = 50;
        private Pen _gridLine { get; init; } = new Pen(Color.Black, 1);
        private int _gridSizeInit { get; set; } = 500;

        public frmGridLine()
        {
            InitializeComponent();

            comboBox1.Items.Add(_gridSizeInit);
            comboBox1.Items.Add(501);
            comboBox1.SelectedIndex = comboBox1.FindStringExact(_gridSizeInit.ToString());

            SetPictureBoxSize(_gridSizeInit);
        }

        private void SetPictureBoxSize(int size)
        {
            pictureBox1.Width = size;
            pictureBox1.Height = size;
        }

        private void comboBox1_SelectionChangeCommitted(object sender, EventArgs e)
        {
            int size = Convert.ToInt32(comboBox1.Text);
            SetPictureBoxSize(size);
            pictureBox1.Refresh();
        }

        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            DrawGridLine(e.Graphics);
        }

        private void DrawGridLine(Graphics g)
        {
            RectangleF bound = g.ClipBounds;
            int boundWidth = (int)bound.Width;
            int boundHeight = (int)bound.Height;

            for (Point topLeft = new Point(0, 0); topLeft.Y <= boundHeight; topLeft.Offset(0, _cellLength))
                g.DrawLine(_gridLine, topLeft, new Point(boundWidth, topLeft.Y));

            for (Point topLeft = new Point(0, 0); topLeft.X <= boundWidth; topLeft.Offset(_cellLength, 0))
                g.DrawLine(_gridLine, topLeft, new Point(topLeft.X, boundWidth));
        }
    }
}

執行效果

• 延伸閱讀
• [C#] 繪圖 - 九宮格
• 參考資料
• Point.Offset 方法