NETCore3Demo/ConsoleApp4/Program.cs

using ClassLibrary1;
using System;
using System.Linq;
using System.Reflection;

namespace ConsoleApp4
{
    class Program
    {
        static void Main(string[] args)
        {

            Assembly assembly = Assembly.GetCallingAssembly();
            var typesWithMyAttribute =
              from t in assembly.GetTypes()
              let attributes = t.GetCustomAttributes(typeof(CosmosDBAttribute), false)
              where attributes != null && attributes.Length > 0
              select new { Type = t, Attributes = attributes.Cast<CosmosDBAttribute>() };
            Console.WriteLine("Hello World!");
        }


    }
}