C# Online Compiler | .NET Fiddle

using System;
					
public class Program
{
	public static void Main()
	{
		ConcreteClass C = new ConcreteClass();
		
		C.DoSomethingElse3();
		
	}
	public interface Iinterface
	{
	    void DoSomething();
		void DoSomethingElse();
		void DoSomethingElse1();
		//customer dont want to implemnet below ones
		void DoSomethingElse2(); 
		void DoSomethingElse3();
	}
	
	//Solution 1 : create an abstract class 
	public abstract class MyClass: Iinterface 
	{
		public void DoSomething(){}
	    public void DoSomethingElse(){}
		public void DoSomethingElse1(){}
		
		// Mark those Abstract which you dont want to implement 
		public  abstract void DoSomethingElse2();
		public abstract void DoSomethingElse3();
	   	
	
	}
	
	//Solution 2 : Use these keywords NotImplementedException/NotSupportedException
	public class ConcreteClass : Iinterface
	{
		public void DoSomething(){}
	    public void DoSomethingElse(){}
		public void DoSomethingElse1(){}
		
		// keywords NotImplementedException/NotSupportedException
		public  void DoSomethingElse2()
		{
			throw new NotSupportedException();
		}
		
		public  void DoSomethingElse3()
		{
		    throw new NotImplementedException();
		}
		
	
	}
	// Solution 3 : Segregate interface into logical units this should how we design our application in the beginning,
	
	
}

    // Solution 3 : Segregate interface into logical units this should how we design our application in the beginning,
 
using System;
                    
public class Program
{
    public static void Main()
    {
        ConcreteClass C = new ConcreteClass();
        
        C.DoSomethingElse3();
        
    }
    public interface Iinterface
    {
        void DoSomething();
        void DoSomethingElse();
        void DoSomethingElse1();
        //customer dont want to implemnet below ones
        void DoSomethingElse2(); 
        void DoSomethingElse3();
    }
    
    //Solution 1 : create an abstract class 
    public abstract class MyClass: Iinterface 
    {