Is it possible to make an anonymous class inherit another class?

Question

This is a long shot, but I have a funny coding situation where I want the ability to create anonymous classes on the fly, yet be able to pass them as a parameter to a method that is expecting an interface or subclass. In other words, I'd like to be able to do something like this:

public class MyBase { ... }

public void Foo(MyBase something)
{
  ...
}

...
var q = db.SomeTable.Select(t =>
        new : MyBase // yeah, I know I can't do this...
        {
          t.Field1,
          t.Field2,
        });
foreach (var item in q)
  Foo(item);

Is there any way to do this other than using a named class?

You *could* use `dynamic` as parameter type instead of `MyBase` but I would strongly suggest not doing that for anything that has even the remote chance of being called from more than one place. — Dirk, Mar 06 '14 at 14:07

score 63 · Accepted Answer · answered Mar 06 '14 at 14:07

63

No. Anonymous types always implicitly derive from object, and never implement any interfaces.

From section 7.6.10.6 of the C# 5 specificiation:

An anonymous object initializer declares an anonymous type and returns an instance of that type. An anonymous type is a nameless class type that inherits directly from object.

So if you want a different base class or you want to implement an interface, you need a named type.

answered Mar 06 '14 at 14:07

Jon Skeet

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Spookily I was thinking about this earlier except with interfaces. Maybe even at the time this question was asked... :) – Chris Mar 06 '14 at 23:47

Shlomi Borovitz · Answer 2 · 2014-03-06T14:27:45.657

8

No. From the documentation:

Anonymous types are class types that derive directly from object, and that cannot be cast to any type except object.

To solve your problem, just replace the anonymous type with normal class...

edited Mar 06 '14 at 14:27

answered Mar 06 '14 at 14:10

Shlomi Borovitz

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score 2 · Answer 3 · answered Mar 06 '14 at 14:11

2

Cannot extend an anonymous but you could declare your method to accept a dynamic parameter if you really need this to work.

answered Mar 06 '14 at 14:11

T McKeown

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score 1 · Answer 4 · answered Aug 26 '19 at 10:07

1

Short answer: no

Long answer: You could use a C# proxy class. There are several tools that can proxy classes. For example Moqs. https://github.com/moq/moq4

answered Aug 26 '19 at 10:07

Anders

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Is it possible to make an anonymous class inherit another class?

4 Answers4