How can I convert string into int without enumerating a query

Question

Probably I'm blind, but I can't find how to convert string to int. I wrote

query.OrderByDescending(a => SqlFunctions.IsNumeric(
    a.Index.Substring(a.Index.Length - 4, 4)) == 1 ?
    Convert.ToInt32(a.Index.Substring(a.Index.Length - 4, 4)) :
    0);

But, as I suspected, it returns an error

LINQ to Entities does not recognize the method 'Int32 ToInt32(System.String)'

Moreover SqlFunctions don't have a member Convert. Is any way to achieve this without enumerating the query?

EDIT: int.Parse throws

LINQ to Entities does not recognize the method 'Int32 Parse(System.String)

@SriramSakthivel: It was possible that LINQ to Entities knew about `int.Parse` but not about `Convert.ToInt32`. That appears not to be the case, but it was at least possible. — Jon Skeet, Apr 22 '15 at 13:04
Hmm. I've seen other posts that suggest `Convert.ToInt32` *should* work in EF. Interesting. — Jon Skeet, Apr 22 '15 at 13:06
This issue is a bit frustrating. I ran into it just yesterday afternoon. One thing that you have to keep in mind is that EF has to be able to generate the SQL regardless of the provider. For example, the generated SQL may be different between SQL Server and MySQL. It has to be generic enough that it can handle all situations. — Jason Richmeier, Apr 22 '15 at 13:07
Yes, i found it too, that's why i post Convert.ToInt32 instead int.Parse and earned -2 :) — Marcin J, Apr 22 '15 at 13:07
Can you make sort on client (e.g. call `ToArray` for `query`)? Or it works slow for your case? — Vlad, Apr 22 '15 at 13:18
I have many, many records, after sorting I get only 1 page of entities , so it have to be on sql side — Marcin J, Apr 22 '15 at 13:54

Jason Richmeier · Accepted Answer · 2015-04-22T13:13:19.637

4

This is a long shot as I have not tried it myself (I read about it a few weeks ago).

If the SqlFunctions class does not provide a function that you need, you can create a custom function on the SQL Server side and then create a class on the .NET side similar to the SqlFunctions class to call the custom function. There is an attribute that you have to decorate the .NET class with.

Perhaps something like this would work?

You can read more about this here and here.

edited Apr 22 '15 at 13:13

answered Apr 22 '15 at 13:04

Jason Richmeier

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this sounds nice, but like a workaround quite common problem. If no one knows any shorter way that will be the answer. – Marcin J Apr 22 '15 at 13:16
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@MarcinJ Note that if you are using code first instead of edm files, you have to do like http://stackoverflow.com/a/23658354/613130 – xanatos Apr 22 '15 at 13:19

score 0 · Answer 2 · edited Apr 22 '15 at 12:55

0

int a=int.Parse(string);

is the way you can convert a string into int in c#

edited Apr 22 '15 at 12:55

Nagaraj S

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answered Apr 22 '15 at 12:54

xNeyte

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score 0 · Answer 3 · answered Apr 22 '15 at 12:56

0

int.TryParse(X.Number, out tmp) ? tmp : 0

answered Apr 22 '15 at 12:56

BenM

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score 0 · Answer 4 · edited Apr 22 '15 at 19:58

0

Have you tried it with TryParse? something like this:

int number;
query.OrderByDescending(a =>(
                        int.TryParse(a.Item1.Substring(1, 2), 
                                        out number) == true  ? number: 0));

I always use TryParse with lambda expressions.

edited Apr 22 '15 at 19:58

BIBD

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answered Apr 22 '15 at 13:17

paulofer85

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This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post - you can always comment on your own posts, and once you have sufficient [reputation](http://stackoverflow.com/help/whats-reputation) you will be able to [comment on any post](http://stackoverflow.com/help/privileges/comment). – JNYRanger Apr 22 '15 at 14:03
@JNYRanger ok i wanted to comment his post but i realize that i don t have enough reputation. I thought it was one possible solution to his question. I ll ve it in mind for next time. – paulofer85 Apr 22 '15 at 14:06
1

Sorry, @JNRanger - I think its a reasonable attempt at an answer. – BIBD Apr 22 '15 at 19:56

How can I convert string into int without enumerating a query

4 Answers4