Combine Lambda-Expressions dynamic for where

Question

I have a list of lambda-expressions List<Func<SomeObject, bool>> filterList; This filterlist is using to filter a collection of SomeObject easily like this:

List<SomeObject> randomList; //filled with random stuff

foreach (Func<SomeObject, bool> filter in filterlist)
    randomList = randomList.Where(filter).ToList();

Now I want to combine some filters - but I want to combine them with AND- or OR-Statements. As example: The user has 3 filter A,B and C and want to combine them to something like "A && (B || C).

I have no idea howto do this.

How would you know when to combine with AND and when to do it with OR? — Matias Cicero, Jul 29 '16 at 12:27
Yeah, but I want to setup complex filter (example "A && (B || C)"). :P — akop, Jul 29 '16 at 12:30
My filterlist contains also a name and id. The user chose two filter (B and C) and press a button "combine OR". Now I want to identificate the two rules and combine them to a new single rule. — akop, Jul 29 '16 at 12:33

score 2 · Accepted Answer · answered Jul 29 '16 at 12:26

You are using Func<T>, not Expression<Func<T>>, which makes it impossible to 'rewrite' them, or combine multiple func's in a single one. So you can only execute them in a certain order.

You are already combining them with AND.

To combine two (or more) criteria with OR, do this:

randomList = randomList.Where(x => filter1(x) || filter2(x)).ToList();

To do A && (B || C), do this:

randomList = randomList.Where(x => filterA(x) && (filterB(x) || filterC(x))).ToList();

Ok, when I use `Expression>` - how can I "rewrite" them? – akop Jul 29 '16 at 12:36 — akop, Jul 29 '16 at 12:36

Combine Lambda-Expressions dynamic for where

1 Answers1