CODEWITHSUNDEEP
c#entity-frameworkexceptionlinq-to-sql
Grant
Grant

Reputation: 11366

E.F. NotSupportedException - Transition from LINQ2SQL

i am making the transition from LINQ2SQL to EF and am having some trouble with some basic lambda expressions.

In the following example, I am trying to retrieve a basic list of client related data. This statement when run using a LINQ2SQL data context works fine.

var data = db.Clients.Select(c => c.Id + ":" + c.Firstname);
foreach (var item in data)
{

}

When i execute it against an EF data context i get:

 NotSupportedException - Unable to cast the type 'System.Int32' to type 'System.Object'. LINQ to Entities only supports casting EDM primitive or enumeration types.

NB: the Id field is an integer.

I have been able to fix the error by adding a ToArray() after db.Clients.

Can someone please explain if..

a) I need to make this kind of code change to every pre-exisitng statement in my solution to get it working with EF; and

b) Why does EF have so much trouble with a basic concatenation when LINQ2SQL was fine?

thanks.

Upvotes: 0

Views: 112

Answers (1)

p.s.w.g
p.s.w.g

Reputation: 149050

I can't tell you why it works in Linq2SQL and not in Entity Framework, but I can help you solve your issue.

I suggest you use the SqlFunctions.StringConvert function.

var data = db.Clients.Select(c => 
    SqlFunctions.StringConvert((double)c.Id) + ":" + c.Firstname);

Personally, if I have to do any string manipulation, I try to place that only in my client code, like this:

var data = db.Clients.Select(c => { c.Id, c.Firstname });
foreach (var item in data)
{
    var stringData = String.Format("{0}:{1}", item.Id, item.Firstname);
    ...
}

Upvotes: 0

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