diff --git a/Examples/Program_CollectAccessHash.cs b/Examples/Program_CollectAccessHash.cs
new file mode 100644
index 0000000..e51f824
--- /dev/null
+++ b/Examples/Program_CollectAccessHash.cs
@@ -0,0 +1,75 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text.Json;
+using System.Threading.Tasks;
+using TL;
+
+namespace WTelegramClientTest
+{
+	class Program_CollectAccessHash
+	{
+		private const string StateFilename = "SavedState.json";
+		private const long DurovID = 1006503122; // known ID for Durov's Channel
+		private static SavedState savedState = new();
+
+		// go to Project Properties > Debug > Environment variables and add at least these: api_id, api_hash, phone_number
+		static async Task Main(string[] _)
+		{
+			Console.WriteLine("The program demonstrate how load/save/use collected access hash.");
+			WTelegram.Helpers.Log = (l, s) => System.Diagnostics.Debug.WriteLine(s);
+			using var client = new WTelegram.Client(Environment.GetEnvironmentVariable);
+			client.CollectAccessHash = true;
+
+			if (File.Exists(StateFilename))
+			{
+				Console.WriteLine("Loading previously saved access hashes from disk...");
+				using (var stateStream = File.OpenRead(StateFilename))
+					savedState = await JsonSerializer.DeserializeAsync<SavedState>(stateStream);
+				foreach ((long id, long access_hash) in savedState.Channels) client.SetAccessHashFor<Channel>(id, access_hash);
+				foreach ((long id, long access_hash) in savedState.Users) client.SetAccessHashFor<User>(id, access_hash);
+			}
+
+			Console.WriteLine("Connecting to Telegram...");
+			await client.ConnectAsync();
+			await client.LoginUserIfNeeded();
+
+			var durovAccessHash = client.GetAccessHashFor<Channel>(DurovID);
+			if (durovAccessHash != 0)
+			{
+				// we already know the access hash for Durov's Channel, so we can directly use it
+				Console.WriteLine($"Channel @durov has ID {DurovID} and access hash was already collected: {durovAccessHash:X}");
+			}
+			else
+			{
+				Console.WriteLine("Resolving channel @durov to get its ID, access hash and other infos...");
+				var durovResolved = await client.Contacts_ResolveUsername("durov"); // @durov = Durov's Channel 
+				if (durovResolved.peer.ID != DurovID)
+					throw new Exception("@durov has changed channel ID ?!");
+				durovAccessHash = client.GetAccessHashFor<Channel>(DurovID); // should have been collected from the previous API result
+				if (durovAccessHash == 0)
+					throw new Exception("No access hash was automatically collected !? (shouldn't happen)");
+				Console.WriteLine($"Channel @durov has ID {DurovID} and access hash was automatically collected: {durovAccessHash:X}");
+			}
+
+			Console.WriteLine("With the access hash, we can now join the channel for example.");
+			await client.Channels_JoinChannel(new InputChannel { channel_id = DurovID, access_hash = durovAccessHash });
+
+			Console.WriteLine("Channel joined. Press any key to save and exit");
+			Console.ReadKey(true);
+
+			Console.WriteLine("Saving all collected access hashes to disk for next run...");
+			savedState.Channels = client.AllAccessHashesFor<Channel>().ToList();
+			savedState.Users = client.AllAccessHashesFor<User>().ToList();
+			using (var stateStream = File.Create(StateFilename))
+				await JsonSerializer.SerializeAsync(stateStream, savedState);
+		}
+
+		class SavedState
+		{
+			public List<KeyValuePair<long, long>> Channels { get; set; } = new();
+			public List<KeyValuePair<long, long>> Users { get; set; } = new();
+		}
+	}
+}
diff --git a/src/Client.cs b/src/Client.cs
index 6cfc81f..c71847f 100644
--- a/src/Client.cs
+++ b/src/Client.cs
@@ -1220,10 +1220,10 @@ namespace WTelegram
 			=> _accessHashes.GetValueOrDefault(typeof(T));
 		/// <summary>Retrieve the access_hash associated with this id (for a TL class)</summary>
 		/// <typeparam name="T">a TL object class. For example User, Channel or Photo</typeparam>
-		public long? GetAccessHashFor<T>(long id) where T : ITLObject
+		public long GetAccessHashFor<T>(long id) where T : ITLObject
 		{
 			lock (_accessHashes)
-				return _accessHashes.GetOrCreate(typeof(T)).TryGetValue(id, out var access_hash) ? access_hash : null;
+				return _accessHashes.GetOrCreate(typeof(T)).TryGetValue(id, out var access_hash) ? access_hash : 0;
 		}
 		public void SetAccessHashFor<T>(long id, long access_hash) where T : ITLObject
 		{