我尝试过.DrawCurve和.DrawBezier,但结果并不完全是一个弧.

我能做什么？

解：

经过几个小时的代码写作,我用这个算法绘制了我想要的(给出3点a,b,c和一个GraphicsPath路径)：

double d = 2 * (a.X - c.X) * (c.Y - b.Y) + 2 * (b.X - c.X) * (a.Y - c.Y);
double m1 = (Math.Pow(a.X,2) - Math.Pow(c.X,2) + Math.Pow(a.Y,2) - Math.Pow(c.Y,2));
double m2 = (Math.Pow(c.X,2) - Math.Pow(b.X,2) + Math.Pow(c.Y,2) - Math.Pow(b.Y,2));
double nx = m1 * (c.Y - b.Y) + m2 * (c.Y - a.Y);
double ny = m1 * (b.X - c.X) + m2 * (a.X - c.X);
double cx = nx / d;
double cy = ny / d;
double dx = cx - a.X;
double dy = cy - a.Y;
double distance = Math.Sqrt(dx * dx + dy * dy);
Vector va = new Vector(a.X - cx,a.Y - cy);
Vector vb = new Vector(b.X - cx,b.Y - cy);
Vector vc = new Vector(c.X - cx,c.Y - cy);
Vector xaxis = new Vector(1,0);
float startAngle = (float)Vector.AngleBetween(xaxis,va);
float sweepAngle = (float)(Vector.AngleBetween(va,vb) + Vector.AngleBetween(vb,vc));
path.AddArc(
    (float)(cx - distance),(float)(cy - distance),(float)(distance * 2),startAngle,sweepAngle);