Int.Parse is not supported by LINQ to Entities

Question

var result = from m in db.BDClassInfo
                 join n in db.BDProfessionInfo on m.ProfessionInfoKey equals n.ProfessionInfoKey
                 join o in db.BDInstitute on n.InstituteKey equals o.InstituteKey
                 where o.InstituteKey == instituteKey
                 && int.Parse(m.EntranceYear) + n.LearnLen > int.Parse(currentTerm.TermNo.Substring(0, 4))
                 select new { m, n.ProfessionInfoName, o.InstituteName };

 

I know that LINQ to Entities does not support Int.Parse function, I want to know is there any solution to solve the problem in other way?

Like the problem above, behind the "where", the function Int.Parse is necessary.

Answer 1

。。。搞了半天发到中文论坛上来了，我还以为是英文论坛呢

Answer 2

Moved to English forums as requested

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Answer 3

Hello a4712635,

 

Welcome to the MSDN Forum.

I think you are right. By testing, I found that fi you use int.Parse, then you will got an exception because Method 'Int32 Parse(System.String)' has no supported translation to SQL.

However, we can use Convert.ToInt32(). It works fine in my programe. In your case, we can modify it to the following:

Convert.ToInt32(m.EntranceYear) + n.LearnLen > Convert.ToInt32(currentTerm.TermNo.Substring(0, 4))

Actually, i also found the difference between Convert.ToInt32() and  int.Parse(). Here they are:

If you've got a string, and you expect it to always be an integer (say, if some web service is handing you an integer in string format), you'd use Int32.Parse(). If you're collecting input from a user, you'd generally user Int32.TryParse(), since it allows you more fine-grained control over the situation when the user enters in invalid input.

Convert.ToInt32() takes an object as its argument, and I believe it invokes Int32.TryParse() when it finds that the object taken as the argument is a string. Convert.ToInt32 also does not throw ArgumentNullException when it's argument is null the way Int32.Parse() does. That also means that Convert.ToInt32() is probably a wee bit slower than Int32.Parse() because it has to ask its argument what it's type is.

If you have any questions please feel free to let us know.

 

Have a nice day,

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Jackie Sun [MSFT]
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Answer 4

Thanks very much!

Answer 5

It's my pleasure~ :)

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Jackie Sun [MSFT]
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Answer 6

I tried Convert.ToInt32() today, but there is still an exception :

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

my code:

var result = from m in db.BDClassInfo
               join n in db.BDProfessionInfo on m.ProfessionInfoKey equals n.ProfessionInfoKey
               join o in db.BDInstitute on n.InstituteKey equals o.InstituteKey
               where o.InstituteKey == "01"
               && Convert.ToInt32(m.EntranceYear) + n.LearnLen > Convert.ToInt32(currentterm.Substring(0, 4))
               select new { m, n.ProfessionInfoName, o.InstituteName };

Answer 7

How about modifing your code like this:

var result = from m in db.BDClassInfo.AsEnumerable() ?

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Jackie Sun [MSFT]
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Please remember to mark the replies as answers if they help and unmark them if they provide no help.

Answer 8

Thank you, AsEnumerable() is OK

What does AsEnumerable() mean?

Answer 9

:) You are welcome.

Please see this.

http://msdn.microsoft.com/en-us/library/bb335435.aspx

And in this topic contains a list of CLR methods that can be converted to command tree canonical functions and executed on the server:

http://msdn.microsoft.com/en-us/library/bb738681.aspx

For CLR methods not on this list, you would have to pull the results down to the client using .AsEnumerable() and execute a LINQ to Objects query.

 

Thanks,

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Jackie Sun [MSFT]
MSDN Community Support | Feedback to us
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Please remember to mark the replies as answers if they help and unmark them if they provide no help.