动态linq查询选项

Question

我将一个表单序列化为json对象，如下所示

Fruit: Apple,
StrawberyParam: "test",
AppleParam: 1,
PeachParam: 3,
Car: Porsche
BugattiParam:3,
PorscheParam: "gas",
ToyotaParam: "go",
AnotherParam: "test1"

基本上，用户选择水果和汽车，参数在其他属性中描述。

我正在考虑编写不同的where子句并将它们连接起来创建一个字符串，然后像这样应用。tolist:

StrawberryWhere = ....
AppleWhere = ....
PeachWhere = ....
PorscheWhere = ....
.....

然后这样写:

MyQuery = fromClause + switch based on Fruit and Car selected
          (ie. AppleWhere + PorscheWhere) + selectClause;
MyQuery.ToList();

是这样做的吗?我用的是linq-to-sql，我对这个框架不是很熟悉，谢谢你的建议

Answer 1

你不会使用字符串，你会这样做:

Expression<Func<TSource, bool>> appleWhere = x => x.Fruit == Fruits.Apple;
Expression<Func<TSource, bool>> porscheWhere = x => x.Car == Cars.Porsche;
// ...
var result = jsonObjects.Where(appleWhere).Where(porscheWhere).ToList();

Answer 2

看看Dynamic LINQ:

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