Graphics

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Drawing2D;

namespace FillTriangle
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            
            GraphicsPath gp = new GraphicsPath(FillMode.Winding);
            
            gp.AddLine(new PointF(290, 170),new PointF(98, 128));

            gp.AddLine(new PointF(110, 170), new PointF(290, 170));

            gp.AddLine(new PointF(110, 170), new PointF(98, 128));

            g.FillPath(new SolidBrush(Color.Red), gp);
        }
    }
}