C# Online Compiler | .NET Fiddle

using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;

public class Program
{
	private const int NumberInsertedKeys = 5000;
	public static Hashtable hTable = new Hashtable();
	public static Dictionary<int, string> dict = new Dictionary<int, string>();
	public static decimal MemoryUsed;
	public static decimal DictionaryMemoryUsed;
	public static decimal HashtableMemoryUsed;
	public static Stopwatch watch = new Stopwatch();
	public static void Main()
	{
		Console.WriteLine("Dictionary VS Hashtable");
		MemoryUsed = System.GC.GetTotalMemory(true) / 1024;
		Msg("Started with this: {0:N0} KB", MemoryUsed);

		DictionaryTest();
		HashtableTest();
		CollectMemory();
	}

	private static void CollectMemory()
	{
		GC.Collect();
		Console.WriteLine("\nMemory used after full collection: {0:N0}", GC.GetTotalMemory(true) / 1024);
	}

	private static void DictionaryTest()
	{
		Msg("\n--------- Results for {0}", "Dictionary");
		watch.Start();
		InsertDataForDictionary();
		watch.Stop();
		Msg("Insert time taken (minutes): {0} or about {1} minutes and {2} seconds and milliseconds {3}", watch.Elapsed.TotalMinutes, watch.Elapsed.Minutes, watch.Elapsed.Seconds, watch.Elapsed.Milliseconds);
		DictionaryMemoryUsed = (System.GC.GetTotalMemory(true) / 1024) - MemoryUsed - HashtableMemoryUsed;
		Msg("MemoryUsed: {0:N0} KB", DictionaryMemoryUsed);
		watch = Stopwatch.StartNew();
		ReadEachElementOfDictionary();
		watch.Stop();
		Msg("Read time taken (minutes): {0} or about {1} minutes and {2} seconds and milliseconds {3}", watch.Elapsed.TotalMinutes, watch.Elapsed.Minutes, watch.Elapsed.Seconds, watch.Elapsed.Milliseconds);
	}

	private static void HashtableTest()
	{
		Msg("\n--------- Results for {0}", "Hashtable");
		watch = Stopwatch.StartNew();
		InsertDataForHashTable();
		watch.Stop();
		Msg("Insert time taken (minutes): {0} or about {1} minutes and {2} seconds and milliseconds {3}", watch.Elapsed.TotalMinutes, watch.Elapsed.Minutes, watch.Elapsed.Seconds, watch.Elapsed.Milliseconds);
		HashtableMemoryUsed = (System.GC.GetTotalMemory(true) / 1024) - MemoryUsed - DictionaryMemoryUsed;
		Msg("MemoryUsed: {0:N0} KB", HashtableMemoryUsed);
		watch = Stopwatch.StartNew();
		ReadEachElementOfHashTable();
		watch.Stop();
		Msg("Read time taken (minutes): {0} or about {1} minutes and {2} seconds and milliseconds {3}", watch.Elapsed.TotalMinutes, watch.Elapsed.Minutes, watch.Elapsed.Seconds, watch.Elapsed.Milliseconds);
	}

	private static void Msg(string name, params object[] args)
	{
		Console.WriteLine(name, args);
	}

	private static Dictionary<int, string> InsertDataForDictionary()
	{
		for (int i = 0; i < NumberInsertedKeys; i++)
		{
			dict.Add(i, "Test data " + i);
		}

		return dict;
	}

	private static void ReadEachElementOfDictionary()
	{
		for (int i = 0; i < dict.Count; i++)
		{
			var value = dict[i];
		}
	}

	private static Hashtable InsertDataForHashTable()
	{
		for (int i = 0; i < NumberInsertedKeys; i++)
		{
			hTable.Add(i, "Test data " + i);
		}

		return hTable;
	}

	private static void ReadEachElementOfHashTable()
	{
		for (Int64 i = 0; i < hTable.Count; i++)
		{
			var value = hTable[i];
		}
	}
}

 
using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
​
public class Program
{
    private const int NumberInsertedKeys = 5000;
    public static Hashtable hTable = new Hashtable();
    public static Dictionary<int, string> dict = new Dictionary<int, string>();
    public static decimal MemoryUsed;
    public static decimal DictionaryMemoryUsed;
    public static decimal HashtableMemoryUsed;
    public static Stopwatch watch = new Stopwatch();
    public static void Main()
    {
        Console.WriteLine("Dictionary VS Hashtable");
        MemoryUsed = System.GC.GetTotalMemory(true) / 1024;
        Msg("Started with this: {0:N0} KB", MemoryUsed);
​
        DictionaryTest();
        HashtableTest();
        CollectMemory();
    }