5

At first,I do not use dynamic,I just use the code like this,and it works well.

  List<Student> result2 = StudentRepository.GetStudent(sex,age).ToList();
  IQueryable rows2 = result2.AsQueryable();

But when I change it to dynamic，it is wrong.

 dynamic result = GetPeopleData(sex,age);
 IQueryable rows = result.AsQueryable();

and I add a method like this,I build the project it show that List do not have the AsQueryable method.How to change it?

 private dynamic GetPeopleData(int sex, int age)
    {
        if(sex>30)
            return StudentRepository.GetStudent(sex,age).ToList();
        else
            return TeacherRepository.GetTeacher(sex, age).ToList();
    }
Cœur
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flower
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    Why would you want to make it dynamic? – Jeroen Vannevel Mar 06 '15 at 03:51
  • You are showing the `GetPeopleData` method, but you call the `GetStudentData`. Is it right? – aush Mar 06 '15 at 03:57
  • Because I just want to get the data,not matter it come from student or teacher,I just want to change them to IQueryable rows and them export these rows. – flower Mar 06 '15 at 04:02
  • http://stackoverflow.com/questions/5311465/extension-method-and-dynamic-object-in-c-sharp ? – Alexei Levenkov Mar 06 '15 at 04:02
  • Go read up on inheritance and polymorphism. There is no reason why you should need to use `dynamic` here. You should almost never need to use `dynamic`. Also, what is the point of creating an `IQueryable` from a `List`? Calling `ToList()` on your repository eagerly fetches all records and loads them into memory; you lose any opportunity for query operators to execute on the server. – Mike Strobel Mar 09 '15 at 20:00

2 Answers2

5

AsQueryable() is an extension method and those don't work on dynamic.

Depending on what you want to do, there are several possible solutions:

  1. Don't use dynamic. Instead, make Student and Teacher implement a common interface (say, IPerson) and use that:

    private IReadOnlyList<IPerson> GetPeopleData(int sex, int age)
{
    if (sex > 30)
        return StudentRepository.GetStudent(sex, age).ToList();
    else
        return TeacherRepository.GetTeacher(sex, age).ToList();
}

…

var result = GetPeopleData(sex, age);
IQueryable<IPerson> rows = result2.AsQueryable();

  2. Call AsQueryable() as a normal static method:

    dynamic result = GetPeopleData(sex, age);
IQueryable rows = Queryable.AsQueryable(result);

BTW, checking whether sex is over 30 doesn't make any kind of sense to me. You should probably rethink that part of your design.

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svick
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  • That possibly depends on what `sex` means here. I would rather not ask for more details. – Wiktor Zychla Mar 06 '15 at 13:45
  • @WiktorZychla The only alternative I can think of certainly couldn't be used to reliably distinguish between students and teachers. :-) – svick Mar 06 '15 at 13:56
-2

It is similar to this question.

As @jbtule said,Anonymous types are internal, if you cross assembly boundaries dynamic can't resolve the property.

Rather than using an anonymous type, try using an actual type or an Expando Object.

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Lyly
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    I don't believe this applies as OP did not show any usage of anonymous types... (assuming `GetTeacher` returns `List` similar to the other one). – Alexei Levenkov Mar 06 '15 at 04:45