CollectUsersChats helper for your dictionaries (min-aware). CollectAccessHash won't collect 'min' access_hash.

Examples/Program_ListenUpdates.cs

@@ -29,8 +29,7 @@ namespace WTelegramClientTest
 				if (dialogsBase is Messages_Dialogs dialogs)
 					while (dialogs.dialogs.Length != 0)
 					{
-						foreach (var (id, user) in dialogs.users) _users[id] = user;
-						foreach (var (id, chat) in dialogs.chats) _chats[id] = chat;
+						dialogs.CollectUsersChats(_users, _chats);
 						var lastDialog = dialogs.dialogs[^1];
 						var lastMsg = dialogs.messages.LastOrDefault(m => m.Peer.ID == lastDialog.Peer.ID && m.ID == lastDialog.TopMessage);
 						var offsetPeer = dialogs.UserOrChat(lastDialog).ToInputPeer();
@@ -50,8 +49,7 @@ namespace WTelegramClientTest
 		private static void Client_Update(IObject arg)
 		{
 			if (arg is not UpdatesBase updates) return;
-			foreach (var (id, user) in updates.Users) _users[id] = user;
-			foreach (var (id, chat) in updates.Chats) _chats[id] = chat;
+			updates.CollectUsersChats(_users, _chats);
 			foreach (var update in updates.UpdateList)
 				switch (update)
 				{

FAQ.md

@@ -61,6 +61,8 @@ So you can just pass that structure you already have, in place of the `Input...`
 * If you have enabled the [CollectAccessHash system](EXAMPLES.md#collect-access-hash) at the start of your session, it will have collected the `access_hash`.
 You can then retrieve it with `client.GetAccessHashFor<User/Channel/Photo/Document>(id)`
 
+⚠️ *`access_hash` obtained from a User or Channel with flag `min` may not be used for most requests. See [Min constructors](https://core.telegram.org/api/min).*
+
 <a name="dev-versions"></a>
 #### 5. I need to test a feature that has been developed but not yet released in WTelegramClient nuget
 

src/Client.cs

@@ -1175,11 +1175,16 @@ namespace WTelegram
 			lock (_accessHashes)
 				_accessHashes.GetOrCreate(typeof(T))[id] = access_hash;
 		}
+		static readonly FieldInfo userFlagsField = typeof(User).GetField("flags");
+		static readonly FieldInfo channelFlagsField = typeof(Channel).GetField("flags");
 		internal void CollectField(FieldInfo fieldInfo, object obj, object access_hash)
 		{
 			if (fieldInfo.Name != "access_hash") return;
 			if (access_hash is not long accessHash) return;
 			var type = fieldInfo.ReflectedType;
+			if ((type == typeof(User) && ((User.Flags)userFlagsField.GetValue(obj)).HasFlag(User.Flags.min)) ||
+				(type == typeof(Channel) && ((Channel.Flags)channelFlagsField.GetValue(obj)).HasFlag(Channel.Flags.min)))
+				return; // access_hash from Min constructors are mostly useless. see https://core.telegram.org/api/min
 			if (type.GetField("id") is not FieldInfo idField) return;
 			if (idField.GetValue(obj) is not long id)
 				if (idField.GetValue(obj) is not int idInt) return;

src/TL.Helpers.cs

@@ -518,6 +518,38 @@ namespace TL
 		}
 	}
 
+	public static class Helpers
+	{
+		private class CollectorPeer : Peer
+		{
+			public override long ID => 0;
+			internal Dictionary<long, User> _users;
+			internal Dictionary<long, ChatBase> _chats;
+			internal override IPeerInfo UserOrChat(Dictionary<long, User> users, Dictionary<long, ChatBase> chats)
+			{
+				lock (_users)
+					foreach (var user in users.Values)
+						if (user != null)
+							if (!user.flags.HasFlag(User.Flags.min) || !_users.TryGetValue(user.id, out var prevUser) || prevUser.flags.HasFlag(User.Flags.min))
+								_users[user.id] = user;
+				lock (_chats)
+					foreach (var kvp in chats)
+						if (kvp.Value is not Channel channel)
+							_chats[kvp.Key] = kvp.Value;
+						else if (!channel.flags.HasFlag(Channel.Flags.min) || !_chats.TryGetValue(channel.id, out var prevChat) || prevChat is not Channel prevChannel || prevChannel.flags.HasFlag(Channel.Flags.min))
+							_chats[kvp.Key] = channel;
+				return null;
+			}
+		}
+
+		/// <summary>Accumulate users/chats found in this structure in your dictionaries, ignoring <see href="https://core.telegram.org/api/min">Min constructors</see> when the full object is already stored</summary>
+		/// <param name="structure">The structure having a <c>users</c></param>
+		/// <param name="users"></param>
+		/// <param name="chats"></param>
+		public static void CollectUsersChats(this IPeerResolver structure, Dictionary<long, User> users, Dictionary<long, ChatBase> chats)
+			=>  structure.UserOrChat(new CollectorPeer { _users = users, _chats = chats });
+	}
+
 	public static class Markdown
 	{
 		/// <summary>Converts a <a href="https://core.telegram.org/bots/api/#markdownv2-style">Markdown text</a> into the (Entities + plain text) format used by Telegram messages</summary>

src/TL.cs

@@ -13,7 +13,7 @@ namespace TL
 	public interface IMethod<ReturnType> : IObject { }
 	public interface IPeerResolver { IPeerInfo UserOrChat(Peer peer); }
 
-	public static class Serialization
+	internal static class Serialization
 	{
 		internal static void WriteTLObject<T>(this BinaryWriter writer, T obj) where T : IObject
 		{