Example
interface BaseInterface {}
class BaseClass : BaseInterface {}
interface DerivedInterface {}
class DerivedClass : BaseClass, DerivedInterface {}
var baseInterfaceType = typeof(BaseInterface);
var derivedInterfaceType = typeof(DerivedInterface);
var baseType = typeof(BaseClass);
var derivedType = typeof(DerivedClass);
var baseInstance = new BaseClass();
var derivedInstance = new DerivedClass();
Console.WriteLine(derivedInstance is DerivedClass); //True
Console.WriteLine(derivedInstance is DerivedInterface); //True
Console.WriteLine(derivedInstance is BaseClass); //True
Console.WriteLine(derivedInstance is BaseInterface); //True
Console.WriteLine(derivedInstance is object); //True
Console.WriteLine(derivedType.BaseType.Name); //BaseClass
Console.WriteLine(baseType.BaseType.Name); //Object
Console.WriteLine(typeof(object).BaseType); //null
Console.WriteLine(baseType.IsInstanceOfType(derivedInstance)); //True
Console.WriteLine(derivedType.IsInstanceOfType(baseInstance)); //False
Console.WriteLine(
string.Join(",",
derivedType.GetInterfaces().Select(t => t.Name).ToArray()));
//BaseInterface,DerivedInterface
Console.WriteLine(baseInterfaceType.IsAssignableFrom(derivedType)); //True
Console.WriteLine(derivedInterfaceType.IsAssignableFrom(derivedType)); //True
Console.WriteLine(derivedInterfaceType.IsAssignableFrom(baseType)); //False