LINQ：SelectMany的反向功能

Question

SelectMany允许将数组展平为单个数组

如何实现反向功能？将单个数组拆分为等长X的数组？最后一个数组的元素数可能少于X。

var lst = new List<int> { val1, val2, ... valN }

foreach (var g in lst.<some-magic>)
{
   // g - is array like {val1, val2, val3}, for the next iteration it is {val4, val5, val6}, ... 

}