Test if object implements interface

Question

What is the simplest way of testing if an object implements a given interface in C#? (Answer to this question in Java)

Solution 1

if (object is IBlah)

or

IBlah myTest = originalObject as IBlah

if (myTest != null)

Solution 2

Using the is or as operators is the correct way if you know the interface type at compile time and have an instance of the type you are testing. Something that no one else seems to have mentioned is Type.IsAssignableFrom:

if( typeof(IMyInterface).IsAssignableFrom(someOtherType) )
{
}

I think this is much neater than looking through the array returned by GetInterfaces and has the advantage of working for classes as well.

Solution 3

If you want to use the typecasted object after the check:
Since C# 7.0:

if (obj is IMyInterface myObj)

This is the same as

IMyInterface myObj = obj as IMyInterface;
if (myObj != null)

See .NET Docs: Pattern matching overview

Solution 4

For the instance:

if (obj is IMyInterface) {}

For the class:

Check if typeof(MyClass).GetInterfaces() contains the interface.

Solution 5

A variation on @AndrewKennan's answer I ended up using recently for types obtained at runtime:

if (serviceType.IsInstanceOfType(service))
{
    // 'service' does implement the 'serviceType' type
}

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