可选参数和命名参数

为什么这两个要一起讲，因为这两个常常一起出现，可选参数常常用来替代以前的重载，但是当多个可选参数出现的时候，你想显示传递的参数只有一个，这个时候编译器不知道你想给那个参数传递参数，就需要指定传递那个参数的名字，这个就是命名参数

 private RectangleFigure CreateFigure(Color color, PointF pointF = new PointF(), SizeF sizeF = new SizeF(),int priority = basicPriority)
 {
            color = Color.FromArgb(alpha, color.R, color.G, color.B);
            RectangleFigure figure;
            if (pointF.IsEmpty || sizeF.IsEmpty)
            {
                float w = Math.Min(canvas.ClientRectangleWorld.Width, backDie.Width) / 10;
                float h = Math.Min(canvas.ClientRectangleWorld.Height, backDie.Height) / 10;
                float x = (canvas.ClientRectangleWorld.Left + canvas.ClientRectangleWorld.Right - w) / 2;
                float y = (canvas.ClientRectangleWorld.Top + canvas.ClientRectangleWorld.Bottom - h) / 2;
                figure = new RectangleFigure(new RectangleF(x, y, w, h));
            }
            else
            {
                figure = new RectangleFigure(new RectangleF(pointF, sizeF));
            }
            figure.nLayer = priority;
 }

比如我只想传递Priority 参数，那么就必须要用命名参数

editingRectangle = CreateFigure(color,priority:priority);