Why this Conditional operator error?

Question

Possible Duplicate:
Conditional operator assignment with Nullable<value> types?

Hi, Why this doesn't work?

  DateTime? SomeNullableDateTime = string.IsNullOrEmpty("") ? null : Convert.ToDateTime("01/02/1982");

Is it an error somewhere? The problem seems to be the null because

  DateTime? SomeNullableDateTime = string.IsNullOrEmpty("") ? Convert.ToDateTime("01/02/1982") : Convert.ToDateTime("01/02/1982");

Works fine..

Thanks

There are quite a few duplicates of this - look in the Related bar on the RHS. — Jon Skeet, May 05 '11 at 11:59
Even "doesn't want to compile" isn't an appropriate error description. You already got quite some rep, you should really know this by now — Daniel Hilgarth, May 05 '11 at 12:02

CodeNaked · Accepted Answer · 2011-05-05T12:03:42.540

2

Both conditional values need to be of the same type or allow implicit conversion from one type to another, like so:

DateTime? SomeNullableDateTime = string.IsNullOrEmpty("") ? (DateTime?)null : Convert.ToDateTime("01/02/1982");

More information can be found here, but to summarize:

Either the type of first_expression and second_expression must be the same, or an implicit conversion must exist from one type to the other.

edited May 05 '11 at 12:03

answered May 05 '11 at 11:58

CodeNaked

Can you cast a DateTime to DateTime? directly like that? That's neat if you can.. – Kieren Johnstone May 05 '11 at 11:59
@Kieren Johnstone: Yup, you can. – BoltClock May 05 '11 at 12:00
@Kieren - Yes you can, but it's actually not needed in this case as there is an implicit conversion. – CodeNaked May 05 '11 at 12:00
"need to be of the same type" - actually the rules are a little more involved. – H H May 05 '11 at 12:02
@Henk - Correct, updated to indicate implicit conversions are allowed. – CodeNaked May 05 '11 at 12:04

score 0 · Answer 2 · answered May 05 '11 at 11:59

0

Because null and Convert.ToDateTime are not the same type.

You can use this:

DateTime? SomeNullableDateTime = string.IsNullOrEmpty("") ? (DateTime?)null : new DateTime?(Convert.ToDateTime("01/02/1982"));

answered May 05 '11 at 11:59

Kieren Johnstone

2 Answers2