null exception for tuple in C# even after adding a null check

Asked Dec 16 '21 at 21:06

Active Dec 16 '21 at 21:26

Viewed 54 times

I have the following code:

var allUsers = new List<string>();
var response = await context
  .CallActivityAsync<(List<string> names, int grade)>( "Function", null);          

if (response != null) allUsers.AddRange(response.names);

response is a tuple. it is giving a null exception. How to handle null exception for tuple in C#?

edited Dec 16 '21 at 21:26

asked Dec 16 '21 at 21:06

user989988

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1

Where do you define and initialize `allUsers`? It's probably null. – Jonathan Wood Dec 16 '21 at 21:08
1

@ZoharPeled: Yes, I missed `response.entities`. But if `allUsers` was null, why wouldn't you get an error on this line? – Jonathan Wood Dec 16 '21 at 21:10
Updated the code. Please see above. – user989988 Dec 16 '21 at 21:10
3

@ZoharPeled `response` cannot be `null` because it's a value tuple. – juharr Dec 16 '21 at 21:12
@juharr yeah, I've missed that myself :-) too late here to be working on code, I guess. – Zohar Peled Dec 16 '21 at 21:13
I'm sorry help me understand what I am missing? – user989988 Dec 16 '21 at 21:22
Use the debugger to find out what is null! [Point to stuff and look at the tooltip](https://i.stack.imgur.com/4eWny.png) – Caius Jard Dec 16 '21 at 21:32
1

You can't `AddRange(null)`. While your `response` object is not `null`, `response.names` MIGHT be `null`. That will generate the exception you're seeing. I made a simple test for this at https://dotnetfiddle.net/cocWKs – 3Dave Dec 16 '21 at 21:57
So, change your `if (response != null)` to `if (response.names != null)`. – 3Dave Dec 16 '21 at 22:01
@3Dave I'm not the OP.. I was just pointing out how they can help themselves (or help us help them) – Caius Jard Dec 16 '21 at 22:01
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@CaiusJard My mistake. I never learned to read... :) – 3Dave Dec 16 '21 at 22:02

null exception for tuple in C# even after adding a null check

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