How to union with a scalar value - entity-framework

Question

In this pseudo-code, the last line won't work because the scalar value isn't IQueryable.
var scalarValue = 7;
var qry = (from t in db.Table
where t.Filter == 5 //Arbitrary
select t.ID);
var unioned = qry.Union(scalarValue);
It's straightforward in SQL:
select t.ID
from Table
union
select 7;
In my scenario I do need to select a valid Table.ID, so the workaround is:
var scalarValue = 7;
var qry = (from t in db.Table
where t.Filter == 5 //Arbitrary
select t.ID);
var scalarQry = (from t in db.Table
where t.ID == scalarValue
select t.ID);
var unioned = qry.Union(scalarQry);
However, if there is a way to output "select 7;" for example, then that's what I'm after for this question.

Answer 1

Writing
MyContext.MyClass.Select(t => t.Id).Union(new List<long>() { 42 }).ToList();
produces the following SQL query (MyClass is a DbSet<MyClass>) :
SELECT
[Distinct1].[C1] AS [C1]
FROM ( SELECT DISTINCT
[UnionAll1].[MyClassId] AS [C1]
FROM (SELECT
[Extent1].[MyClassId] AS [MyClassId]
FROM [dbo].[MyClasss] AS [Extent1]
UNION ALL
SELECT
cast(42 as bigint) AS [C1]
FROM ( SELECT 1 AS X ) AS [SingleRowTable1]) AS [UnionAll1]
) AS [Distinct1]
The overload of Union which gets called is :
public static IQueryable<TSource> Union<TSource>(this IQueryable<TSource> source1, IEnumerable<TSource> source2)
in System.Linq.Queryable
I hope this will match your needs