$filter 用法:
1，Return all products with category equal to “Toys”. http://localhost/Products?$filter=Category eq 'Toys'
2，Return all products with price less than 10. http://localhost/Products?$filter=Price lt 10
3，Logical operators: Return all products where price >= 5 and price <= 15.
http://localhost/Products?$filter=Price ge 5 and Price le 15
4，String functions: Return all products with “zz” in the name. http://localhost/Products?$filter=substringof('zz',Name)
5，Date functions: Return all products with ReleaseDate after