Daily Coding Problem: Problem #1, C#

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/*Good morning! Here's your coding interview problem for today.
This problem was recently asked by Google.
Given a list of numbers and a number k, return whether any two numbers from the list add up to k.
For example, given [10, 15, 3, 7] and k of 17, return true since 10 + 7 is 17.
Bonus: Can you do this in one pass?*/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Assert(IsThere(new List<int>(){10, 15, 3, 7}, 17), true, "TEST 1");
            Assert(IsThere(new List<int>(){10, 15, 3, 7}, 19), false, "TEST 2");
            Assert(IsThere(new List<int>(){10, 10}, 20), true, "TEST 3");
            Assert(IsThere(new List<int>(){10}, 20), false, "TEST 4");
            Assert(IsThere(new List<int>(){}, 20), false, "TEST 5");
            Assert(IsThere(new List<int>(){-5, 5}, 0), true, "TEST 6");
            Assert(IsThere(new List<int>(){-5, 6}, 6), false, "TEST 7");
        }
        
        static bool IsThere(List<int> list, int k)
        {
            var dic = list.GroupBy(f => f).ToDictionary(f => f.Key, z => z.Count());
            foreach(var el in list)
            {
                var need = k - el;
                if(need == el && dic[el] == 1)
                {
                    continue;
                }
                if(dic.ContainsKey(need))
                {
                    return true;
                }
            }
            return false;
        }
        static void Assert(bool value, bool shouldBe, string info)
        {
            if(value == shouldBe)
            {
                Console.WriteLine(info + " passed.");
            }
            else
            {
                Console.WriteLine(info + " failed.");
            }                
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,19 sec, absolute running time: 0,11 sec, cpu time: 0,09 sec, average memory usage: 15 Mb, average nr of threads: 3