Use array of ints parameter in FromSQL query and Where In clause - entity-framework-core

Question

I have a list of ints:
var ids = new List { 10, 20 };
And I need to find Users with that ids:
context.Users.FromSqlInterpolated($#"
select Users.*
where Users.Id in ({String.Join(',', ids)})"
But I get the following error:
'Conversion failed when converting the nvarchar value '10, 20' to data type int.'
How can I use such a parameter?

Answer 1

Using Interpolated method is not appropriate here, because {String.Join(',', ids)} defines single string placeholder, hence EF Core binds single nvarchar parameter with value '10,20', so the actual SQL is like this
select Users.*
where Users.Id in ('10,20')
which is invalid, hence the exception.
You should use Raw method instead. Either
var query = context.Users.FromSqlRaw($#"
select Users.*
where Users.Id in ({String.Join(',', ids)})");
which will embed literal values
select Users.*
where Users.Id in (10,20)
or if you want to parameterize it, generate parameter placeholders like {0}, {1} etc. inside the SQL and pass values separately:
var placeholders = string.Join(",", Enumerable.Range(0, ids.Count)
.Select(i => "{" + i + "}"));
var values = ids.Cast<object>().ToArray();
var query = context.Users.FromSqlRaw($#"
select Users.*
where Users.Id in ({placeholders})", values);
which would generate SQL like this
select Users.*
where Users.Id in (#p0,#p1)

Answer 2

If you need to combine .FromSql() and SQL WHERE x IN () then perform a second operation on the output IQueryable<T> of the .FromSql() call.
var ids = new List { 10, 20 };
var query = context.Users.FromSqlInterpolated(
$#"select *
from Users");
if (ids?.Count > 0)
{
query = query.Where(user => ids.Contains(user.Id));
}
Resultant SQL approximates to:
select * from (
select *
from Users
) u
where u.Id in (10,20)
No invalid SQL if ids is empty
No empty result if ids is empty string (I was working with a string data type)