using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var counters = new Dictionary<string, ICounter>();

        counters.Add("cntr1", new Counter1());

        counters.Add("cntr2", new Counter2());

        counters.Add("cntr3", null);

        var cf = counters.Where(c => c.Value != null).ToDictionary(c => c.Key, c => c.Value.GetSummary());

        foreach (var keyValuePair in cf.ToList()) {

            Console.WriteLine(keyValuePair.Value);

        }

    }

}

​

internal interface ICounter {

    string GetSummary();

}

​

internal class Counter1 : ICounter {

    public string GetSummary() {

        return "Counter1";

    }

}

​

internal class Counter2 : ICounter {

    public string GetSummary() {

        return "Counter2";

    }

}

​