三角形類：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;

namespace transform
{
    class Triangle
    {
        PointF A, B, C;

        public Triangle(PointF a,PointF b,PointF c)
        {
            A = a;
            B
 
 = b;
            C = c;
        }

        /// <summary>
        /// 繪製三角形
        /// </summary>
        /// <param name="g"></param>
        public void Draw(Graphics g)
        {
            Pen pen = new Pen(Color.Red,5);
            g.DrawLine(pen, A, B);
            g.DrawLine(pen, B
 
, C);
            g.DrawLine(pen, C, A);
        }

        /// <summary>
        /// 三角形旋轉
        /// </summary>
        /// <param name="degrees"></param>
        public void Rotate(int degrees)
        {
            float angle = (float)(degrees / 360f * Math.PI);
            float newX = (float
 
)(A.X * Math.Cos(angle) - A.Y * Math.Sin(angle));
            float newY = (float)(A.X * Math.Sin(angle) + A.Y * Math.Cos(angle));

            A.X = newX;
            A.Y = newY;

            newX = (float)(B.X * Math.Cos(angle) - B.Y * Math.Sin(angle));
            newY = (float)(B.X * Math.Sin(angle) + B.Y * Math.Cos(angle));

            B.X = newX;
            B.Y = newY;

            newX = (float)(C.X * Math.Cos(angle) - C.Y * Math.Sin(angle));
            newY = (float)(C.X * Math.Sin(angle) + C.Y * Math.Cos(angle));

            C.X = newX;
            C.Y = newY;
        }
    }
}

C# form：

using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace transform
{
    public partial class Form1 : Form
    {
        Triangle t;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

            PointF A = new PointF(0, -200);
            PointF B = new PointF(200, 200);
            PointF C = new PointF(-200, 200);

            t = new Triangle(A, B, C);
        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            e.Graphics.TranslateTransform(300, 300);
            t.Draw(e.Graphics);
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            t.Rotate(1);
            this.Invalidate();
        }
    }
}

使用C#自帶的視窗程式
1.建立一個三角形類 使用了C#繪製方法
2.form中新增繪製方法，新增一個定時器
3.定時器中需要設定視窗無效 可以實時進行重繪 顯示旋轉
4.開啟雙快取避免顯示一閃一閃