Is there a way to test if a variable is dynamic?

Question

The following piece of code will always return true unless the variable v is null:

v is dynamic

and the following test will not compile ("The typeof operator cannot be used on the dynamic type"):

v.GetType() == typeof(dynamic)

So is there a way to test if the variable is dynamic?

Answer 1

Firstly, you need to separate the variable and the object. A variable is dynamic if it is defined as dynamic. That is all. There is nothing more. A field or property would be annotated with the [Dynamic] attribute, i.e.

public dynamic Foo {get;set;}

is actually:

[Dynamic]
public object Foo {get;set;}

This basically acts as a prompt for the compiler to access the object via the dynamic API rather than via the OOP API.

An object supports full dynamic capabilities if it implements IDynamicMetaObjectProvider - however, such an object can be accessed via both the dynamic API and via the regular OOP API (it can have both). Equally, an object that doesn't implement IDynamicMetaObjectProvider can be accessed via either API (but: only the public members will be available via dynamic).

Answer 2

There is no CLR type called dynamic. The C# compiler makes all dynamic values of type object and then calls custom binding code to figure out how to handle them. If dynamic was used, it will show up as Object.

But You can check if an instance is of type IDynamicMetaObjectProvider or you can check whether the type implements IDynamicMetaObjectProvider

Answer 3

In C# dynamic means no complile-time check and it's gonna have the type of the other side of the = symbol. However GetType is a runtime evaluation, so you always gonna retrieve declared type and not dynamic.

You can read a little bit more here: http://msdn.microsoft.com/en-us/magazine/gg598922.aspx