C# Interface

We have two Classes ClassOne & ClassTwo and two interfaces InterfaceOne and InterfaceTwo.
Is this code valid?

interface InterfaceOne

    {

        void InterfaceOneMethod();

    }



    interface InterfaceTwo

    {

        void InterfaceTwoMethod();

    }



    class ClassOne :  InterfaceOne, ClassTwo 

    {

        public void InterfaceOneMethod()

        {

            //Some Code

        }

    }



    class ClassTwo

    {        

    }

Ans: Base class must come before interface.

class ClassOne :   ClassTwo, InterfaceOne

    {

        public void InterfaceOneMethod()

        {

            //Some Code

        }

    }