GDI draw method

using System.Drawing;
using System.Windows.Forms;

/*
Created by: CodeAssassin
Date: 10/02/2016
Use: To create a simple draw mechanics example using GDI and a panel
*/

namespace SimpleDraw_Panel
{
    internal class SimpleDraw
    {
        private Panel _p;
        private bool MouseIsDown = false;
        private Graphics G;

        public SimpleDraw(Panel p)
        {
            if (p != null)
            {
                _p = p;
                _p.MouseDown += _p_MouseDown;
                _p.MouseUp += _p_MouseUp;
                _p.MouseMove += _p_MouseMove;
                Clear();
            }
        }

        public void Clear()
        {
            if (_p != null)
            {
                G = _p.CreateGraphics();
                G.Clear(Color.White);
                G.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBilinear;
                G.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
                G.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
                _p.Invalidate();
            }
        }

        private void Draw(MouseEventArgs e)
        {
            if (G != null)
            {
                G.DrawRectangle(Pens.Black, new Rectangle(e.X, e.Y, 1, 1));
            }
        }

        private void _p_MouseMove(object sender, MouseEventArgs e)
        {
            if (MouseIsDown)
            {
                Draw(e);
            }
        }

        private void _p_MouseUp(object sender, MouseEventArgs e)
        {
            MouseIsDown = false;
        }

        private void _p_MouseDown(object sender, MouseEventArgs e)
        {
            Draw(e);
            MouseIsDown = true;
        }
    }
}