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Suppose I have a class that looks like this: 

class Derived : // some inheritance stuff here
{
}

I want to check something like this in my code: 

Derived is SomeType;

But looks like is operator need Derived to be variable of type Dervied, not Derived itself. I don't want to create an object of type Derived.
How can I make sure Derived inherits SomeType without instantiating it?

P.S. If it helps, I want something like what where keyword does with generics.
EDIT:
Similar to this answer, but it's checking an object. I want to check the class itself.

Community
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atoMerz
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2 Answers2

329

To check for assignability, you can use the Type.IsAssignableFrom method:

typeof(SomeType).IsAssignableFrom(typeof(Derived))

This will work as you expect for type-equality, inheritance-relationships and interface-implementations but not when you are looking for 'assignability' across explicit / implicit conversion operators.

To check for strict inheritance, you can use Type.IsSubclassOf:

typeof(Derived).IsSubclassOf(typeof(SomeType))
Wernight
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Ani
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    Just as a note to anyone else wondering, this won't return true when checking against generic type/interface definitions, as far as I can tell you need to search the inheritance chain and check for generic type definitions yourself. – Alex Hope O'Connor Sep 23 '15 at 00:59
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    Alex, how would you go about searching the inheritance chain of a generic type to accomplish this? – Douglas Gaskell Nov 12 '15 at 11:07
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    @AlexHopeO'Connor's note is important and I think solution is there http://stackoverflow.com/questions/457676/check-if-a-class-is-derived-from-a-generic-class – Furkan Ekinci May 25 '16 at 11:49
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    For PCL `typeof(SomeType).GetTypeInfo().IsAssignableFrom(typeof(Derived).GetTypeInfo())` – Seafish May 15 '17 at 16:51
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    For those a little confused about the order, such as myself: `typeof(InvalidOperationException).IsAssignableFrom(typeof(Exception)) = false` `typeof(Exception).IsAssignableFrom(typeof(InvalidOperationException)) = true` – Joel Feb 24 '21 at 00:51
23

Try this

typeof(IFoo).IsAssignableFrom(typeof(BarClass));

This will tell you whether BarClass(Derived) implements IFoo(SomeType) or not

Haris Hasan
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