int[] intArray = new int [] { 1, 2, 3 };
var result = from c in sys_Tree
                 where intArray .Contains(c.id)
                 select c;

------解决方案--------------------
int[] intArray = new int [] { 1, 2, 3 };
var result = from c in sys_Tree
                where intArray .Contains(c.id)
                select c;


------解决方案--------------------
  
var result = from c in sys_Tree
                where new int[]{ 1, 2, 3 }.Contains(c.id)
                select c;

OR:

var result =sys_Tree.Where(c=>int[]{ 1, 2, 3 }.Contains(c.id));


------解决方案--------------------
用ls的第二种lambda表达式，看起来舒服

------解决方案--------------------
http://blog.csdn.net/q107770540/article/details/5387946

------解决方案--------------------
from u in sys_Tree  
where u.id.Contains(1,2,3)
select u

------解决方案--------------------
弱弱的表达下，至今我都不懂什么是lambda表达式，但我写的linq跟楼上所写的一样，不知道是也不是