Database objects come from the database library you're using (either LINQ-to-SQL or Entity Framework), they're not originated from F# so they're nullable. The value returned by exactlyOneOrDefault
when there isn't exactly one is null
.
When making a query how do you check if the default value was returned?
-
15-07-2023 - |
문제
Using the code below:
let student =
query {
for student in db.Student do
where (student.StudentID = 1)
select student
exactlyOneOrDefault
}
How do you check the value of student, and just what would be the default value if no match in the database was found?
해결책
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