如何在窗体中制作不同的形状，就像我们在油漆中绘制一样

我正在尝试在窗口形式中绘制不同的形状，就像我们在油漆中绘制一样。我想要的场景，当用户单击矩形按钮，然后在窗体上绘制一个矩形，它应该绘制，所以是绘制手绘形状的情况。下面是我的代码:

    {
        bool shouldPaint = false;
        int initialX;
        int initialY;
        bool rectButton = false;
        bool freeButton = false;
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            shouldPaint = true;
            initialX = e.X;
            initialY = e.Y;
        }
        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            shouldPaint = false;
        }
        if ( (rectButton==true) && (shouldPaint))
            {
                //
                this.Invalidate();
              this.Refresh();
                System.Drawing.Pen pen1 = new          System.Drawing.Pen(System.Drawing.Color.Black);
                Graphics painter = CreateGraphics();
int width = e.X - initialX, height = e.Y - initialY;
                Rectangle rect = new Rectangle(initialX, initialY, width * Math.Sign(width), height * Math.Sign(height));
                painter.DrawRectangle(pen1, rect);

            }
            else if ((freeButton == true) && (shouldPaint))
            {
                //this.Refresh();
              //  this.Invalidate();
                Graphics painter = CreateGraphics();
                painter.FillEllipse(new SolidBrush(Color.Black), e.X, e.Y, 4, 4);

我面临两个问题;第一个是，我可以在正方向上画我的矩形，但当我试着在反方向上画它时，它不起作用。其次，当我点击手绘按钮时，它会在窗体上绘制手绘形状，但当我先点击矩形按钮，然后点击手绘按钮时，它不会绘制任何手绘形状。我是初学者，所以请温柔地帮助我:)

int minX = Math.Min((int)initX, (int)e.X);
 int minY = Math.Min((int)initY, (int)e.Y);
Rectangle rect = new Rectangle(minX,minY width * Math.Sign(width), height * Math.Sign(height));