动态地方使用LINQ to SQL

Question

我试图做一个过滤器“其中”对未选择元素，并在视图模型

这不是条款是，我有：

var UserQuery = (from u in db.USER 
       join c in db.CONSULT on u.IdUser equals c.IdUser 
       select new UserSexViewModel { IdUser= c.IdUser, UserSex=u.Sex}).Distinct(); 

欲由属于对象咨询或

例如，过滤器后面的对象用户通过任何属性后过滤可变UserQuery：

CONSULT.TypeConsul, 
CONSULT.DateCreation, 
USER.Name, 
USER.Age, and many more... 

像这样：

UserQuery.Where(q=>q.CONSULT.TypeConsul==2) or UserQuery.Where(q=>q.USER.Age>16) 

我怎么能这样做呢？

Answer 1

LINQ动态查询库将帮助你。

请参考http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx

Answer 2

var UserQuery = (from u in db.USER 
       join c in db.CONSULT on u.IdUser equals c.IdUser 
       select new UserSexViewModel { IdUser= c.IdUser, UserSex=u.Sex}).Distinct(); 

//伪代码

var specification = PredicateBuilder.True<Consult>();//default: build from this 
specification = PredicateBuilder.And(specification, x => x.TypeConsult == 2); 
var additionalCriterias = ...; 
specification = additionalCriterias == null || additionalCriterias.Length == 0 
        ? specification 
        : GetComposedSpecification(additionalCriterias); 

var users = UserQuery.Where(specification).ToList() 

predicateBuilder @http://www.albahari.com/nutshell/predicatebuilder.aspx有更多的例子