What wrong with this code

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C#

DateTime? someDate = null;

someDate = (bool)CheckBoxExpired.IsChecked ? DateTime.Now : null;

if ((bool)CheckBoxExpired.IsChecked) someDate = DateTime.Now; else someDate = null;

The second line of code gives the following error:

type of conditional expression cannot be determined because there is no implicit conversion between DateTime and Null

The third line is ok.

In my opinion both lines of code are the same, but why do I get an error on the first one?

Posted 12-Mar-15 21:11pm

Jan Bakker

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Praveen Kumar Upadhyay · Accepted Answer · 2015-03-12T21:29:00

Solution 2

Please check below link. It has very clearly explained reason behind this.

http://stackoverflow.com/questions/295833/nullable-type-issue-with-conditional-operator[^]

Posted 12-Mar-15 21:29pm

Praveen Kumar Upadhyay

Comments

Praveen Kumar Upadhyay 13-Mar-15 3:34am

It's because in a ternary operator, the two values must be the same type.

Jan Bakker 13-Mar-15 3:36am

Now it's clear to me.
Thanks.

Maciej Los 13-Mar-15 3:37am

+5!

Praveen Kumar Upadhyay 13-Mar-15 3:39am

Thanks Maciej, actual credit goes to the guys who has posted this solution. Even I was knowing this answer, but he has explained very proper.

Jan Bakker 13-Mar-15 3:42am

The actual answer to my question is:
It's because in a ternary operator, the two values must be the same type.
Short and clear answer, so 5+

Praveen Kumar Upadhyay 13-Mar-15 3:44am

Thanks and welcome

Peter Leow · Accepted Answer · 2015-03-12T21:26:00

Solution 1

Try this:

? DateTime.Now : (DateTime?) null

Posted 12-Mar-15 21:26pm

Peter Leow

Updated 12-Mar-15 21:28pm

v2

Comments

Jan Bakker 13-Mar-15 3:28am

That works, but why is that necessary?
It's not necessary in the the other line of code.

Peter Leow 13-Mar-15 3:34am

http://www.dotnetperls.com/nullable-datetime

Maciej Los 13-Mar-15 3:37am

+5

Peter Leow 13-Mar-15 4:27am

Thank you, Maciej.