using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var blah = new BlahBlah

        {

            Ids = new long[] {1}

        };

        CheckOnNull(blah);

        blah.Ids = null;

        CheckOnNull(blah);

        blah = null;

        CheckOnNull(blah);

    }

    private static void CheckOnNull(BlahBlah blah)

    {

        if(blah is null || blah.Ids?.Any() != true)

        {

            Console.WriteLine("Blah is null or blah ids collection is null or empty.");

        }

        else

        {

            Console.WriteLine("Everything is okay.");

        }   

    }

}

​

public class BlahBlah

{

    public long[] Ids { get;set; }

}