How to concat strings in LINQ while properly dealing with NULL values - linq

Question

I'd like an elegant way to concatenate several columns together using LINQ, but using the + operator or concat() when any of the columns are NULL results in NULL for the value after concatenation.
Is there anything similar to concat() that handles NULL differently, or am I thinking about this in the incorrect way?
Any help is appreciated!
Here is the code I am using:
List<CustomObject> objects = (
from obj in ObjectTable
where obj.Id == Id
select new CustomObject()
{
EnteredBy = obj.EnteredBy,
EntryDate = obj.EntryDate,
WorknoteText =
obj.VchWorkNote1 +
obj.VchWorkNote2 +
obj.VchWorkNote3 +
obj.VchWorkNote4 +
obj.VchWorkNote5 +
obj.VchWorkNote6 +
obj.VchWorkNote7 +
obj.VchWorkNote8 +
obj.VchWorkNote9 +
obj.VchWorkNote10 +
obj.VchWorkNote11 +
obj.VchWorkNote12 +
obj.VchWorkNote13 +
obj.VchWorkNote14 +
obj.VchWorkNote15 +
obj.VchWorkNote16 +
obj.VchWorkNote17 +
obj.VchWorkNote18 +
obj.VchWorkNote19 +
obj.VchWorkNote20
}).ToList();

Answer 1

One option is to use the null coalescing operator:
List<CustomObject> objects = (from o in ObjectTable
where o.Id == Id
select new CustomObject(){
EnteredBy = o.EnteredBy,
EntryDate = o.EntryDate,
WorknoteText =
(o.VchWorkNote1 ?? "") +
(o.VchWorkNote2 ?? "") +
(o.VchWorkNote3 ?? "") +
(o.VchWorkNote4 ?? "") +
...
(o.VchWorkNote20 ?? "")
}).ToList();
Hopefully the generated SQL will use an appropriate translation.

Answer 2

You can use the ?? operator this way :
...
(object.VchWorkNote5 ?? "") +
(object.VchWorkNote6 ?? "") +
(object.VchWorkNote7 ?? "") +
...

Answer 3

How about (object.VchWorkNote1 ?? "") +.....

Answer 4

Can you add a new column to your database? Something like "Keywords" or "FullText"
Define it to have a calculation, that calculation is basically "ISNULL(<Field1>, '') + ISNULL(<Field2>, '')" etc.
Make sure to mark it as persisted, so it doesn't have to calculate each time.
Then you just need to pull down that one field from your table.

Answer 5

there's probably a cleaner way, but first thing that comes to mind would be a quick null to zero length string conversion:
List<CustomObject> objects = (from object in ObjectTable
where object.Id == Id
select new CustomObject(){
EnteredBy = object.EnteredBy,
EntryDate = object.EntryDate,
WorknoteText =
object.VchWorkNote1 ?? "" +
object.VchWorkNote2 ?? "" +
object.VchWorkNote3 ?? "" +
object.VchWorkNote4 ?? "" +
object.VchWorkNote5 ?? "" +
object.VchWorkNote6 ?? "" +
object.VchWorkNote7 ?? "" +
object.VchWorkNote8 ?? "" +
object.VchWorkNote9 ?? "" +
object.VchWorkNote10 ?? "" +
object.VchWorkNote11 ?? "" +
object.VchWorkNote12 ?? "" +
object.VchWorkNote13 ?? "" +
object.VchWorkNote14 ?? "" +
object.VchWorkNote15 ?? "" +
object.VchWorkNote16 ?? "" +
object.VchWorkNote17 ?? "" +
object.VchWorkNote18 ?? "" +
object.VchWorkNote19 ?? "" +
object.VchWorkNote20 ?? ""
}).ToList();