Question

I need to populate a List<string> but when my query returns a null value, no empty string is created in this List.

var maskObj = (from m in context.sistema_DocType_Index
               join n in context.sistema_Indexes on m.indexId equals n.id
               where m.id == docTypeId
               select new maskModel
               {
                    mask = n.mask
               }).ToList();


return Content(""+maskObj.Count());

If this query returns 3 rows, and all of them are NULL, I need 3 empty strings in the list.
Is there any way I can achieve this?

I understand that for Sql Server, NULL is an absence of value. Even NULL == NULL returns false, so how could I proceed?

Answer 1

I think you want something like the following:

mask = n.mask ?? string.Empty

This uses the null-coalescing operator to use string.Empty if n.mask is null.

The SQL generated by entity framework should be similar to this:

COALESCE(MASK, '')

My answer assumes that you are talking about mask being null when you say “If this query returns 3 rows, and all of them are NULL”.