LINQ dynamic query for entity framework

Question

I have two Guid collections:

List<Guid> statuses;
List<Guid> priorities;

How to make the following query:

var result = context.Activity.Where(a => 
    (a.StatusID == statuses[0] || a.StatusID == statuses[1] || ... || a.StatusID == statuses[n]) &&
    (a.PriorityID == priorities[0] || a.PriorityID == priorities[1] || ... || a.PriorityID  == priorities[m]))

Collections could be empty and in this case we shouldn't add an appropriate 'AND' condition. How to do such dynamic query?

UPDATE

Hmm, imagine I need something like this:

List<Func<Activity, bool>> conds = new List<Func<Activity, bool>>();

var result = context.Activity.Where(conds[0] || (conds[1] && conds[2]))

How to do that?

Bazzz · Accepted Answer · 2012-11-29 15:44:53Z

5

First answer based on question
Selects only those Activity objects of which the StatusID is in statusses and the PriorityID is in priorities. Obviously if the collections are empty none of the Activity objects will match the condition.

var result = context.Activity.Where(a => 
    statuses.Contains(a.StatusID) && priorities.Contains(a.PriorityID));

Alternative answer based on @Don Tomato's comment
There must have been a misunderstanding based on the way you formulated the question. However, I think what you want is to add conditions to an IQueryable as required.

List<Func<Activity, bool>> conditions = new List<Func<Activity, bool>>();
// add conditions to the list
// for eaxmple:
// conditions.add(a => statuses.Contains(a.StatusID));
// or 
// conditions.add(a => a.Name == "Don Tomato");

IQueryable query = context.Activity.AsQueryable();
foreach (Func<Activity, bool> condition in conditions)
   query = query.Where(condition);

List<Activity> result = query.ToList();

edited Nov 29, 2012 at 15:44

answered Nov 29, 2012 at 15:13

Bazzz

27k12 gold badges55 silver badges69 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

beyond-code Over a year ago

Agreed, I missed the obvious dammit!

Jodrell Over a year ago

@DonTomato, This should send an SQL [StatusID] IN (<statusID>, ...) to your database server.

Don Tomato Over a year ago

Good answer, thanks!, but this is not quite what I expected. Suppose I'm going to design a very complex query, where, depending on certain conditions, will add or remove different AND and OR conditions. I would like to see a way to construct a query like in Lego constructions. I need to build the filter expression step-by-step with an 'and/or' combination of each part, instead of inventing ingenious and elegant way to solve a simple problem.

beyond-code · Accepted Answer · 2012-11-29 15:14:35Z

0

You can chain where clauses together like this and the end result is that they will be anded together:

var query = context.Activity.Where(o => <condition1>);

if (2ndconditionrequired)
{
    query = query.where(o => <condition2>);
}

query.ToList();

answered Nov 29, 2012 at 15:14

beyond-code

1,4221 gold badge12 silver badges20 bronze badges

Comments

Mario S · Accepted Answer · 2012-11-29 15:15:09Z

0

You could also do it like this:

var result = context.Activity;

if (statuses != null && statuses.Count > 0)
{
    result = results.Where(a => 
        a.StatusID == statuses[0] || a.StatusID == statuses[1] || ... || a.StatusID == statuses[n];
}

if (priorities != null && priorities.Count > 0)
{
    result = results.Where(a => 
        a.PriorityID == priorities[0] || a.PriorityID == priorities[1] || ... || a.PriorityID  == priorities[m]);
}

result.ToList(); // The query won't be executed until here.

But I guess what you really want to do is as @Bazzz answered.

answered Nov 29, 2012 at 15:15

Mario S

12k24 gold badges42 silver badges47 bronze badges

Collectives™ on Stack Overflow

LINQ dynamic query for entity framework

3 Answers 3

3 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related