Please find issue in below code??

Even with Shweta's correction, there's another small issue as well, namely that you'll get a compiler warning that HM.Des() is hiding the inherited method CEO.Des().

To get rid of this warning you can either add the new keyword to HM.Des():

There is slight mistake in your code. When you inherit interfaces and class together then class always comes first in inheritance pattern. Here is your updated code:
 public interface IEmployee
    {
        void Des();
    }


    public class CEO : IEmployee
    {
        public virtual void Des()
        {
            Console.WriteLine("I M CEO");
        }
    }


    public class HM :  CEO, IEmployee
    {
        public void Des()
        {
        }
    }