LINQ lambda - convert int to string

Question

i'm trying to compare a int with a string in the join method of linq lambda, like this:

database.booking.Join(database.address,
                      book => book.bookno,
                      afh => afh.addressid.ToString(),
                       (book, afh) => new { booking = book, add = afh })
                .Where(book => book.address.name == "test");

but i'm getting an error on the ToString():

System.NotSupportedException: LINQ to Entities does not recognize the method 'Int32 ToInt32(System.String)' method, and this method cannot be translated into a store expression.

How do i solve this?

Try to use `SqlFunctions.StringConvert((double)afh.addressid)` instead `ToString();` — Renatas M., Nov 30 '11 at 12:23
@Poku linq-to-entiites does not support any conversions like conert.Tostring() and convert.ToInt32 , convert.ToDatetime.. — Glory Raj, Nov 30 '11 at 12:33
@Poku My best suggestion is first retrive the records from database into list and then do conversion and comparison on that list ..then it works for you... — Glory Raj, Nov 30 '11 at 12:36

score 3 · Accepted Answer · edited May 23 '17 at 11:46

3

Are you working with Linq to SQL? Linq is trying to convert your lambda to sql query. Unfortunately, ToString is not so easily supported.

You can materialize your tables with ToArray() before join, but it can be expensive.

Look at this article and this question.

edited May 23 '17 at 11:46

Community

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answered Nov 30 '11 at 12:13

Piotr Zierhoffer

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as you mention this whould be too expensive in my case :( – Poku Nov 30 '11 at 12:27
Yes, but look at the links - they might be helpful :) – Piotr Zierhoffer Nov 30 '11 at 13:03
the performance is actually not that bad with this solution, so i will this. Thanks! – Poku Nov 30 '11 at 13:39

score 2 · Answer 2 · answered Nov 30 '11 at 12:17

2

Try this:

var bookinger = database.booking.Join(database.address,
                         book => book.bookno,
                         afh => afh.addressid,
                         (book, afh) =>
                         new { booking = book, add = afh })
                     .Where(book => book.address.name == "test")
                     .Select(new { booking, add = add.ToString() });

answered Nov 30 '11 at 12:17

Andrew Hare

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this would fail when compiling. book.bookno = string and afh.addressid = int. – Poku Nov 30 '11 at 12:27

score 1 · Answer 3 · edited Dec 01 '11 at 10:17

1

Have you tried this??

var bookinger = 
    database.booking.Join(database.address,
        book => book.bookno,
        afh => Convert.ToString(afh.addressid),
        (book, afh) =>
        new { booking = book, add = afh })
    .Where(book => book.address.name == "test");

edited Dec 01 '11 at 10:17

DaveShaw

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answered Nov 30 '11 at 13:42

Azhar Khorasany

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Hi Dave. What did you edit in here? Did I made some silly mistake again :P – Azhar Khorasany Dec 01 '11 at 14:10

LINQ lambda - convert int to string

3 Answers3