Bool? not nullable

Question

I have following field in my class:

public bool? EitherObject1OrObject2Exists => ((Object1 != null || Object2 != null) && !(Object1 != null && Object2 != null)) ? true : null;

But in Visual Studio I get an IntelliSense error that there cannot be a conversion between "bool" and "NULL" even though the field is nullable. What do I do wrong? And is there a cleaner way to check if either one of two objects is not null but one of them must be null?

I think you might benefit from reading [Is Your Code Hard to Understand?](http://www.daedtech.com/code-hard-understand/) blog post by Erik Dietrich. — mason, Mar 09 '17 at 16:32
your expression is redundant. not saying this will solve the problem but its redundant. — Ousmane D., Mar 09 '17 at 16:32
Your method simplifies down to just `Object1 != null ^ Object2 != null` — Servy, Mar 09 '17 at 16:36
This question has been asked probably several hundred times on this site. — Eric Lippert, Mar 09 '17 at 16:39
See my answer here http://stackoverflow.com/a/3151584/88656 which contains links to articles I've written about this issue. — Eric Lippert, Mar 09 '17 at 16:40

Steve · Accepted Answer · 2017-03-09T16:44:11.233

5

try

? (bool?) true : null;

the problem is that default bool (true) is not nullable so the case statement are returning different types as far as the compiler is concerned

And you can remove the redundancy as pointed out by Servy

Object1 != null ^ Object2 != null

edited Mar 09 '17 at 16:44

answered Mar 09 '17 at 16:33

Steve

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I know its outside the scope of OP's question, but maybe include a fix for the redundant null check in their expression? – maccettura Mar 09 '17 at 16:39
1

@maccettura done :) – Steve Mar 09 '17 at 16:42
I use bool? so I can use the [Required] data annotation – Palmi Mar 09 '17 at 16:42
@Palmi make sense – Steve Mar 09 '17 at 16:44

Bool? not nullable

1 Answers1