总而言之：
就是在表达式中没有花括号。
IEnumerable<Rect> rectlist3 = rectlist.Select(rect =>newRect(rect.X + 2, rect.Y, rect.rect.Width, rect.rect.Height));
因此=>接翻译成：
Func(Rect rect, out Rect a)
{
return rect =>newRect(rect.X + 2, rect.Y, rect.rect.Width, rect.rect.Height);
}
IEnumerable<Rect> rectlist4 = rectlist.Where(rect => rect.X>5);
Func(Rect rect, out bool a)
{
return rect => rect.X>5;
}
IEnumerable<Rect> rectlist6=rectlist4.OrderBy(rect=>rect.Y);
Func(Rect rect, out int a)
{
return rect=>rect.Y
}