Question

I’ve got an error:

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

The piece of code:

plist= plist.Where(p => Convert.ToInt(p.Period) >= syslockPeriod);

p.Period example: 201206

pList is IQueryable. p.Period is string typed. sysLockPeriod is int.

How to fix it?

Answer 1

LINQ to entities will try to translate Convert.ToInt32() into SQL instructions, because it’s not one of the known methods it can translate then it’ll generate that error.

You have some workaround but for all of them you have to change your code. Let’s see what you can do (in order of preference, for me).

• Convert Period property/field to the proper type. If it’s an integer type then why you store it in your DB as a string?
• Create a function (in your database) to perform the conversion and use a calculated property (or a view). LINQ to Entities will now have a true column of the proper type (no need to convert) or a function to call (on SQL side) to do the conversion. See this example on MSDN about how to call custom database functions.
• Convert IQueryable to IList with ToList() before Where(), now the where clause will be executed locally and not on the database (this may be something terrible to do if the list is pretty big).