How to convert a class to dynamic parent interface?

I have a generic interface IFoo<>, and a class Bar that implements several interfaces such as IFoo<Class1>, IFoo<Class2> and IFoo<Class3>. I can get the IFoo<ClassX> type using:

Type foo = typeof(IFoo).MakeGenericType({typeOfOneOfTheClasses})

It's sure that a Bar instance can be convert to foo type. I've tried Convert.ChangeType() but failed.

How can I convert a object to one of its parent interfaces dynamically?