if (input1 == "список")
                    {
                        var chatId = message.Chat.Id;
                        var membersCount = await client.GetChatMemberCountAsync(chatId);
                        var random = new Random();
                        var randomIndex = random.Next(membersCount);
                        var members = await client.GetChatMemberAsync(chatId); //ошибка здесь
                        var randomMember = members[randomIndex];
                        await client.SendTextMessageAsync(
                            chatId,
                            $"Random member: {randomMember.FirstName} {randomMember.LastName} ({randomMember.Username})");
                    }