How to check if array is not null in LINQ?

Question

I Have this where statement in LINQ:

(users != null && users.Contains(x.Appointment.UserId))

users is an int[]. When i run this code i have an exception:

Unable to create a null constant value of type 'System.Int32[]'. Only entity types, enumeration types or primitive types are supported in this context.

What should i do?

Don't you need to use the ToList() before attempting the Contains? — Dr Schizo
– Dr Schizo, Commented Jul 30, 2014 at 10:12
Show your real code or example code that demonstrates the problem — Sayse
– Sayse, Commented Jul 30, 2014 at 10:14
This is LINQ-to-SQL or Entity-Framework, right? It looks like it's attempting to translate this Where query to SQL, but the LINQ provider doesn't know how to handle int[] in the DB. — Avner Shahar-Kashtan
– Avner Shahar-Kashtan, Commented Jul 30, 2014 at 10:15
get the null-guard (users != null) out of your EF/LINQ-context ... — Random Dev
– Random Dev, Commented Jul 30, 2014 at 10:18

GuyB · Accepted Answer · 2014-12-01 13:11:34Z

1

I had a similar problem. Assuming you are starting with something like this:

var filtered = appointments
    .Where(x => users != null && users.Contains(x.Appointment.UserId));

As @CarstenKönig suggests, try moving the null check outside of the Where clause:

var filtered = users != null ? 
    appointments.Where(x => users.Contains(x.Appointment.UserId)) :
    appointments;

That means the null check is handled by C#, and LINQ to Entities doesn't attempt to convert it to SQL.

answered Dec 1, 2014 at 13:11

GuyB

1311 silver badge10 bronze badges

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

Comments

Volodymyr · Accepted Answer · 2023-01-05 18:05:26Z

0

As others suggested you could move bool check outside the closure and use resulting bool in your Where statement:

var usersNotNull = users != null;
var users = users == null ? new string[0] : users;
query.Where(x => usersNotNull && users.Contains(x.Appointment.UserId));

edited Jan 5, 2023 at 18:05

answered Jan 5, 2023 at 17:58

Volodymyr

1,2711 gold badge16 silver badges28 bronze badges

Collectives™ on Stack Overflow

How to check if array is not null in LINQ?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related