C# Predicate builder with using AND with OR

Question

I have the following class:

public class testClass
{
    public string name { get; set; }
    public int id { get; set; }
    public int age { get; set; }
}

and the following code:

            var list = new List<testClass>();
            list.Add(new testClass { name = "name", id = 1, age = 30 });
            list.Add(new testClass { name = "name", id = 2, age = 22 });
            list.Add(new testClass { name = "name", id = 3, age = 20 });
            list.Add(new testClass { name = "name", id = 4, age = 30 });
            list.Add(new testClass { name = "name", id = 5, age = 27 });
            list.Add(new testClass { name = "name", id = 6, age = 30 });

            var qble = list.AsQueryable();

            var pred = PredicateBuilder.New<testClass>();
            pred.Or(x => x.name == "name" && x.id == 1);
            pred.Or(x => x.age == 30);
            var predQuery = qble.AsExpandable().Where(pred);

My aim is to create a query that returns all records where:

id = 1 and name = "name"

OR

age = 30

So for the query above, it should return the items at index 0, 1, 5

For the above query it does as I want.

However, I now want to the build the predicate by combining a set of queries, rather than explicitly defining them. So I now have the following 2 queries:

var query1 = list.Where(x => x.name == "name" && x.id == 1);
var query2 = list.Where(x => x.age == 30);

and I want to build the query based on the variables query1 and query2, without explicitly defining the conditions - as these conditions will be dynamically defined and I do not know what they are,and they will be defined in different places.

My guess is I need to do something like this (continuing from above):

var qble = list.AsQueryable();

var query1 = list.Where(x => x.name == "name" && x.id == 1);
var query2 = list.Where(x => x.age == 30);

var pred = PredicateBuilder.New<testClass>();
pred.Or(query1);
pred.Or(query2);
var predQuery = qble.AsExpandable().Where(pred);

but this is not quite correct as the predicate builder will not accept the query as a parameter.

Can this be done?

Adjoining

Is there a need to separate the queries? – Varico

@Varico I am not sure what you mean? – Adjoining

This sounds like an xy problem. What is it you are actually trying to solve/build? What is the "big picture"? – Newfoundland

@Adjoining I mean Can't you just do x.name == "name" && x.id == 1 || x.age == 30 – Varico

@Newfoundland I am trying to create an dynamic OR clause – Adjoining

@Varico no because the and clause is being built up in one place and then I need to check against a further condition and combine the results – Adjoining

Is someting like this? #782839 – Joubert

@Newfoundland it does not have to be predicates. I one place I am building up an AND clause, and then further down the line I need to check if either the AND clause is true, or if a further conditions is true – Adjoining

What do you mean by "Dynamic"? Is this a function and consumer of function will provide two filter expressions? – Corsair

@Corsair By dynamic I mean the where clause is built up using a function depending on what parameters are passed into the query, and then added to the query – Adjoining

@Adjoining Is there any reason you can't use Union? – Tager

@Tager the query could be very big and I do not want it to run twice, I want to build it up and then run it once – Adjoining

Answer 1

You could create two Predicate<T> and invoke them in your .Where call at the end.

var qble = list.AsQueryable();

var query1 = new Predicate<testClass>(x => x.name == "name" && x.id == 1);
var query2 = new Predicate<testClass>(x => x.age == 30);

var predQuery = qble.AsExpandable().Where(x => query1(x) || query2(x));

Or you could build another Predicate<T> beforehand and use this

var query = new Predicate<testClass>(x => query1(x) || query2(x));
var predQuery = qble.AsExpandable().Where(query);

Inequitable