How to safely convert to Integer possible null values

Question

var data = mockDataDB.Data.AsQueryable()
   .Select(x => new ProductDto
   {
       Id = Convert.ToInt64(x.id), // this might fail because id might be null 
       Quantity = Int32.TryParse(x.quantity, out int somenumber) ? x.quantity : (int?)null
   }

Issue with this code is that x.id and x.quantity might be null sometimes, they are both of type string and id and quantity are type of int64 and int32..

How could I safely solve this?

Thanks

cheers

@AhmedAbdelhameed strings which might be null, and in case when they are not null I want to convert them to integers.. — Roxy'Pro, Oct 22 '19 at 13:53
Shouldn't that be `Int32.TryParse(x.quantity, out int somenumber) ? somenumber : (int?)null`? And how exactly does that not work? — juharr, Oct 22 '19 at 13:53
`Id = int.TryParse(x.id, out int myID) ? myID : 0;` something along those lines should work. — Trevor, Oct 22 '19 at 13:54
@juharr but what should I put on somenumber, why I can't use something more generic / dynamic? — Roxy'Pro, Oct 22 '19 at 13:54
@Roxy'Pro if the parse succeeds, it would be `x.id` otherwise it returns `0`... — Trevor, Oct 22 '19 at 13:55
`myID` is the integer that the string `x.id` parsed to, if it parsed successfully. If `x.id` were `"56"` then `myID` would be `56`. — Joshua Robinson, Oct 22 '19 at 13:56
If `Quantity` is a `int` and not a `int?` then you obviously cannot set it to `(int?)null`. You just have to decide what to set it to if the parsing fails. — juharr, Oct 22 '19 at 13:57
Possible duplicate of [Better way to cast object to int](https://stackoverflow.com/questions/745172/better-way-to-cast-object-to-int) or https://stackoverflow.com/questions/4620565/int-tryparse-syntatic-sugar or https://stackoverflow.com/questions/1019793/how-can-i-convert-string-to-int — Trevor, Oct 22 '19 at 13:59
Please post the class definition, I'm interested in knowing the types of `x.Id` and `x.Quantity` — Flater, Oct 22 '19 at 14:08
@Roxy'Pro: Then you are wrong about your claim that `x.Quantity` can be null, as `long` is not a nullable type — Flater, Oct 22 '19 at 14:10

Jonathon Chase · Accepted Answer · 2019-10-22T14:00:21.357

1

You could inline a TryParse with a ternary expression, provided you have a default value in mind for Id when it's null.

var data = mockDataDB.Data.AsQueryable()
   .Select(x => new ProductDto
   {
       Id = Int64.TryParse(x.id, out long val) ? val : 0L, 
       Quantity = Int32.TryParse(x.quantity, out int somenumber) ? somenumber : (int?)null
   }

edited Oct 22 '19 at 14:00

answered Oct 22 '19 at 13:55

Jonathon Chase

9,396
21
39

but what is out long val and out int somenuber? – Roxy'Pro Oct 22 '19 at 13:55
@Roxy'Pro Those are declaring an [out parameter](https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/out-parameter-modifier#calling-a-method-with-an-out-argument) as an inline value. – Jonathon Chase Oct 22 '19 at 13:57
@Roxy'Pro Those are the variables that contain the result of the parsing if it succeeds. – juharr Oct 22 '19 at 13:58
@juharr Why it cant be Quantity or Id which I'm trying to assing value to? – Roxy'Pro Oct 22 '19 at 14:06
1

@Roxy'Pro Properties and indexers can't be passed as out parameters. – Jonathon Chase Oct 22 '19 at 14:10

score 0 · Answer 2 · answered Oct 22 '19 at 13:55

0

Something like this: Id = Int64.TryParse(x.id, out int somenumber) ? somenumber : 0

answered Oct 22 '19 at 13:55

Alexander Powolozki

637
4
12

ziga1337 · Answer 3 · 2019-10-23T12:26:53.103

-1

Edited: You should check if the String variable (x.id) is null. If it is, you set it to zero or some default value that you would want. If its not, proceed with the converting. For example:

Id = (x.id == null) ? 0 : Convert.ToInt64(x.id);

edited Oct 23 '19 at 12:26

answered Oct 22 '19 at 14:02

ziga1337

144
1
10

`x.id.length()` that check if `x.id` is `null` will still throw an exception, because `id` is null... and the `equals` check is wrong – Trevor Oct 22 '19 at 14:04
@Çöđěxěŕ `string.IsNullOrWhiteSpace(x.id)` does the job as well. – Alexander Powolozki Oct 22 '19 at 14:14
1

@AlexanderPowolozki there's more than one way, my comment was based on the answer's post, it's wrong. – Trevor Oct 22 '19 at 14:16

How to safely convert to Integer possible null values

3 Answers3