diff --git a/Telegram bots/Chat.cs b/Telegram bots/Chat.cs
index b1e38ed..62d0440 100644
--- a/Telegram bots/Chat.cs	
+++ b/Telegram bots/Chat.cs	
@@ -1,4 +1,5 @@
-using System.Text.Json;
+using System.Text;
+using System.Text.Json;
 
 namespace Telegram_bots
 {
@@ -118,38 +119,35 @@ public static Chat FromJSON(string jsonString)
         }
         #endregion
 
-        /// <summary>
-        /// Turns it into a string
-        /// </summary>
-        /// <returns>A string representing the chat</returns>
+        /// <inheritdoc/>
         public override string ToString()
         {
-            string str = string.Empty;
-            str += "Id: ";
-            str += Id;
-            str += ", Type: ";
-            str += Type;
+            StringBuilder builder = new();
+            builder.Append("Id: ");
+            builder.Append(Id);
+            builder.Append(", Type: ");
+            builder.Append(Type);
             if (Title != null)
             {
-                str += ", Title: ";
-                str += Title;
+                builder.Append(", Title: ");
+                builder.Append(Title);
             }
             if (FirstName != null)
             {
-                str += ", First name: ";
-                str += FirstName;
+                builder.Append(", First name: ");
+                builder.Append(FirstName);
             }
             if (LastName != null)
             {
-                str += ", Last name: ";
-                str += LastName;
+                builder.Append(", Last name: ");
+                builder.Append(LastName);
             }
             if (Username != null)
             {
-                str += ", Username: ";
-                str += Username;
+                builder.Append(", Username: ");
+                builder.Append(Username);
             }
-            return str;
+            return builder.ToString();
         }
     }
 
diff --git a/Telegram bots/Keyboards/IKeyboard.cs b/Telegram bots/Keyboards/IKeyboard.cs
new file mode 100644
index 0000000..4c5a7f1
--- /dev/null
+++ b/Telegram bots/Keyboards/IKeyboard.cs	
@@ -0,0 +1,13 @@
+namespace Telegram_bots.Keyboards
+{
+    /// <summary>
+    /// Keyboard
+    /// </summary>
+    public interface IKeyboard
+    {
+        /// <summary>
+        /// Keyboard's buttons
+        /// </summary>
+        IKeyboardButton[][] Keyboard { get; set; }
+    }
+}
\ No newline at end of file
diff --git a/Telegram bots/Keyboards/IKeyboardButton.cs b/Telegram bots/Keyboards/IKeyboardButton.cs
new file mode 100644
index 0000000..9d6a789
--- /dev/null
+++ b/Telegram bots/Keyboards/IKeyboardButton.cs	
@@ -0,0 +1,19 @@
+using System.Text.Json.Serialization;
+using Telegram_bots.Keyboards;
+
+namespace Telegram_bots
+{
+    /// <summary>
+    /// Keyboard's button
+    /// </summary>
+    [JsonDerivedType(typeof(InlineKeyboardButton))]
+    [JsonDerivedType(typeof(KeyboardButton))]
+    public interface IKeyboardButton
+    {
+        /// <summary>
+        /// Button's text
+        /// </summary>
+        [JsonPropertyName("text")]
+        string Text { get; set; }
+    }
+}
\ No newline at end of file
diff --git a/Telegram bots/Keyboards/InlineKeyboard.cs b/Telegram bots/Keyboards/InlineKeyboard.cs
new file mode 100644
index 0000000..66024cb
--- /dev/null
+++ b/Telegram bots/Keyboards/InlineKeyboard.cs	
@@ -0,0 +1,23 @@
+using System.Collections;
+using System.Text.Json.Serialization;
+using System.Xml.Serialization;
+
+namespace Telegram_bots.Keyboards
+{
+    /// <summary>
+    /// Inline keyboard
+    /// </summary>
+    /// <remarks>
+    /// Create an inline keyboard
+    /// </remarks>
+    /// <param name="buttons">Keyboard's buttons</param>
+    [Serializable]
+    public class InlineKeyboard(InlineKeyboardButton[][] buttons) : IKeyboard
+    {
+        /// <summary>
+        /// <inheritdoc/>
+        /// </summary>
+        [JsonPropertyName("inline_keyboard")]
+        public IKeyboardButton[][] Keyboard { get; set; } = buttons;
+    }
+}
diff --git a/Telegram bots/Keyboards/InlineKeyboardButton.cs b/Telegram bots/Keyboards/InlineKeyboardButton.cs
new file mode 100644
index 0000000..8591603
--- /dev/null
+++ b/Telegram bots/Keyboards/InlineKeyboardButton.cs	
@@ -0,0 +1,48 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Text.Json.Serialization;
+using System.Threading.Tasks;
+
+namespace Telegram_bots
+{
+    /// <summary>
+    /// The inline keyboard button
+    /// </summary>
+    [Serializable]
+    public class InlineKeyboardButton : IKeyboardButton
+    {
+        /// <summary>
+        /// <inheritdoc/>
+        /// </summary>
+        [JsonPropertyName("text")]
+        public string Text { get; set; }
+        /// <summary>
+        /// CallbackData of the inline keyboard buttons
+        /// </summary>
+        [JsonPropertyName("callback_data")]
+        public string CallbackData { get; set; }
+
+        /// <summary>
+        /// Create an inline keyboard button
+        /// </summary>
+        /// <param name="text">Button's text</param>
+        /// <param name="callbackData">CallbackData of the inline keyboard buttons</param>
+        public InlineKeyboardButton(string text, string callbackData)
+        {
+            Text = text;
+            CallbackData = callbackData;
+        }
+
+        /// <summary>
+        /// Create an inline keyboard button
+        /// </summary>
+        /// <param name="text">Button's text</param>
+        public InlineKeyboardButton(string text)
+        {
+            Text = text;
+            CallbackData = text;
+        }
+    }
+}
diff --git a/Telegram bots/Keyboards/KeyboardButton.cs b/Telegram bots/Keyboards/KeyboardButton.cs
new file mode 100644
index 0000000..c45ad24
--- /dev/null
+++ b/Telegram bots/Keyboards/KeyboardButton.cs	
@@ -0,0 +1,21 @@
+using System.Text.Json.Serialization;
+
+namespace Telegram_bots.Keyboards
+{
+    /// <summary>
+    /// Keyboard button
+    /// </summary>
+    /// <remarks>
+    /// Create a keyboard button
+    /// </remarks>
+    /// <param name="text">Button's text</param>
+    [Serializable]
+    public class KeyboardButton(string text) : IKeyboardButton
+    {
+        /// <summary>
+        /// <inheritdoc/>
+        /// </summary>
+        [JsonPropertyName("text")]
+        public string Text { get; set; } = text;
+    }
+}
\ No newline at end of file
diff --git a/Telegram bots/Keyboards/ReplyKeyboard.cs b/Telegram bots/Keyboards/ReplyKeyboard.cs
new file mode 100644
index 0000000..f2886f0
--- /dev/null
+++ b/Telegram bots/Keyboards/ReplyKeyboard.cs	
@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Text.Json.Serialization;
+using System.Threading.Tasks;
+
+namespace Telegram_bots.Keyboards
+{
+    /// <summary>
+    /// Keyboard
+    /// </summary>
+    /// <remarks>
+    /// Create a keyboard
+    /// </remarks>
+    /// <param name="buttons">Keyboard's buttons</param>
+    [Serializable]
+    public class ReplyKeyboard(KeyboardButton[][] buttons) : IKeyboard
+    {
+        /// <summary>
+        /// <inheritdoc/>
+        /// </summary>
+        [JsonPropertyName("keyboard")]
+        public IKeyboardButton[][] Keyboard { get; set; } = buttons;
+    }
+}
diff --git a/Telegram bots/Keyboards/ReplyKeyboardRemove.cs b/Telegram bots/Keyboards/ReplyKeyboardRemove.cs
new file mode 100644
index 0000000..98aed92
--- /dev/null
+++ b/Telegram bots/Keyboards/ReplyKeyboardRemove.cs	
@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Text.Json.Serialization;
+using System.Threading.Tasks;
+
+namespace Telegram_bots.Keyboards
+{
+    /// <summary>
+    /// Remove the keyboard
+    /// </summary>
+    [Serializable]
+    public class ReplyKeyboardRemove : IKeyboard
+    {
+        /// It's nothing
+        [JsonIgnore]
+        public IKeyboardButton[][] Keyboard { get; set; } = [[]];
+        /// <summary>
+        /// Should I remove the keyboard or not?
+        /// </summary>
+        [JsonPropertyName("remove_keyboard")]
+        public bool RemoveKeyboard { get; set; } = true;
+    }
+}
diff --git a/Telegram bots/Message.cs b/Telegram bots/Message.cs
index bf44fa3..e2e0bbe 100644
--- a/Telegram bots/Message.cs	
+++ b/Telegram bots/Message.cs	
@@ -1,4 +1,5 @@
-using System.Text.Json;
+using System.Text;
+using System.Text.Json;
 
 namespace Telegram_bots
 {
@@ -21,13 +22,21 @@ public class Message
         public required Chat Chat { get; set; }
 
         /// <summary>
-        /// The text of the message
+        /// The Text of the message
         /// </summary>
         public string? Text { get; set; }
         /// <summary>
         /// The sender of the message
         /// </summary>
         public User? From { get; set; }
+        /// <summary>
+        /// Parameters for responding to a message
+        /// </summary>
+        public ReplyParameters? ReplyParameters { get; set; }
+        /// <summary>
+        /// The message that this message responds to
+        /// </summary>
+        public Message? ReplyMessage { get; set; }
 
         #region bool Equals(object? obj)
         /// <summary>
@@ -72,6 +81,14 @@ public static Message FromJSON(JsonDocument jsonDocument)
             {
                 message.From = User.FromJSON(from);
             }
+            if (json.TryGetProperty("reply_to_message", out JsonElement replyMessage))
+            {
+                message.ReplyMessage = FromJSON(replyMessage);
+            }
+            if (json.TryGetProperty("reply_parameters", out JsonElement replyParameters))
+            {
+                message.ReplyParameters = ReplyParameters.FromJSON(replyParameters);
+            }
 
             return message;
         }
@@ -95,31 +112,41 @@ public static Message FromJSON(string jsonString)
         }
         #endregion
 
-        /// <summary>
-        /// Turns it into a string
-        /// </summary>
-        /// <returns>The string representing the message</returns>
+        /// <inheritdoc/>
         public override string ToString()
         {
-            string str = "Id: ";
-            str += Id;
-            str += ", Date: ";
-            str += Datetime;
-            str += ", Chat: (";
-            str += Chat;
-            str += ")";
+            StringBuilder builder = new();
+            builder.Append("Id: ");
+            builder.Append(Id);
+            builder.Append(", Date: ");
+            builder.Append(Datetime);
+            builder.Append(", Chat: (");
+            builder.Append(Chat);
+            builder.Append(')');
             if (Text != null)
             {
-                str += ", Text: ";
-                str += Text;
+                builder.Append(", Text: ");
+                builder.Append(Text);
             }
             if (From != null)
             {
-                str += ", From: (";
-                str += From;
-                str += ")";
+                builder.Append(", From: (");
+                builder.Append(From);
+                builder.Append(')');
+            }
+            if (ReplyParameters != null)
+            {
+                builder.Append(", Reply parameters: (");
+                builder.Append(ReplyParameters);
+                builder.Append(')');
+            }
+            if (ReplyMessage != null)
+            {
+                builder.Append(", Reply to message: (");
+                builder.Append(ReplyMessage);
+                builder.Append(')');
             }
-            return str;
+            return builder.ToString();
         }
 
         /// <summary>
diff --git a/Telegram bots/ReplyParameters.cs b/Telegram bots/ReplyParameters.cs
new file mode 100644
index 0000000..7ca691d
--- /dev/null
+++ b/Telegram bots/ReplyParameters.cs	
@@ -0,0 +1,100 @@
+using System.Text;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace Telegram_bots
+{
+    /// <summary>
+    /// Describes reply parameters for the message that is being sent.
+    /// </summary>
+    [Serializable]
+    public class ReplyParameters
+    {
+        /// <summary>
+        /// Id to reply to the message
+        /// </summary>
+        [JsonPropertyName("message_id")]
+        public long MessageId { get; init; }
+
+        /// <summary>
+        /// The chat_id where the reply message is located
+        /// </summary>
+        [JsonPropertyName("chat_id")]
+        [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+        public long? ChatId { get; set; }
+
+        /// <summary>
+        /// Creates empty parameters for responding to a message
+        /// </summary>
+        public ReplyParameters()
+        {
+            MessageId = 0;
+            ChatId = null;
+        }
+        /// <summary>
+        /// Creates parameters for responding to a message
+        /// </summary>
+        /// <param name="message">The message that needs to be answered</param>
+        public ReplyParameters(Message message)
+        {
+            MessageId = message.Id;
+            ChatId = message.Chat.Id;
+        }
+
+        #region FromJSON
+        /// <summary>
+        /// Create a ReplyParameters from a JsonDocument
+        /// </summary>
+        /// <param name="jsonDocument">JsonDocument</param>
+        /// <returns>ReplyParameters</returns>
+        public static ReplyParameters FromJSON(JsonDocument jsonDocument)
+        {
+            JsonElement json = jsonDocument.RootElement;
+
+            ReplyParameters replyParameters = new()
+            {
+                MessageId = json.GetProperty("message_id").GetInt64(),
+            };
+
+            if (json.TryGetProperty("chat_id", out JsonElement chatId))
+            {
+                replyParameters.ChatId = chatId.GetInt64();
+            }
+
+            return replyParameters;
+        }
+        /// <summary>
+        /// Create a ReplyParameters from a JsonElement
+        /// </summary>
+        /// <param name="rootJsonElement">Root JsonElement</param>
+        /// <returns>ReplyParameters</returns>
+        public static ReplyParameters FromJSON(JsonElement rootJsonElement)
+        {
+            return FromJSON(rootJsonElement.GetRawText());
+        }
+        /// <summary>
+        /// Create a ReplyParameters from a json string
+        /// </summary>
+        /// <param name="jsonString">Json string</param>
+        /// <returns>ReplyParameters</returns>
+        public static ReplyParameters FromJSON(string jsonString)
+        {
+            return FromJSON(JsonDocument.Parse(jsonString));
+        }
+        #endregion
+
+        /// <inheritdoc/>
+        public override string ToString()
+        {
+            StringBuilder builder = new();
+            builder.Append("Message id: ");
+            builder.Append(MessageId);
+            if (ChatId != null)
+            {
+                builder.Append(", Chat id: ");
+                builder.Append(ChatId);
+            }
+            return builder.ToString();
+        }
+    }
+}
diff --git a/Telegram bots/Telegram bots.csproj b/Telegram bots/Telegram bots.csproj
index 2d54e88..deb2cd4 100644
--- a/Telegram bots/Telegram bots.csproj	
+++ b/Telegram bots/Telegram bots.csproj	
@@ -5,7 +5,7 @@
     <RootNamespace>Telegram_bots</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
-    <GenerateDocumentationFile>True</GenerateDocumentationFile>
+    <GenerateDocumentationFile>False</GenerateDocumentationFile>
     <SignAssembly>False</SignAssembly>
     <OutputType>Exe</OutputType>
     <StartupObject>MyTGBot.Tst</StartupObject>
diff --git a/Telegram bots/TelegramBot.cs b/Telegram bots/TelegramBot.cs
index 2d8f1a3..d6be8ed 100644
--- a/Telegram bots/TelegramBot.cs	
+++ b/Telegram bots/TelegramBot.cs	
@@ -1,8 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Net.Http;
-using System.Text.Json;
-using System.Threading.Tasks;
+using System.Text.Json;
 
 namespace Telegram_bots
 {
@@ -15,7 +11,7 @@ public class TelegramBot : IDisposable
         private bool disposedValue;
 
         /// <summary>
-        /// Token for the bot
+        /// token for the bot
         /// </summary>
         protected readonly string Token = string.Empty;
 
@@ -39,7 +35,7 @@ public class TelegramBot : IDisposable
         /// <summary>
         /// A constructor for creating a bot
         /// </summary>
-        /// <param name="Token">Token for the bot</param>
+        /// <param name="token">token for the bot</param>
         /// <exception cref="Exceptions.IncorrectRequestException">Called if you entered the wrong token</exception>
         /// <example>
         /// <code>
@@ -49,12 +45,12 @@ public class TelegramBot : IDisposable
         /// }
         /// </code>
         /// </example>
-        public TelegramBot(string Token)
+        public TelegramBot(string token)
         {
-            this.Token = Token;
+            Token = token;
             httpClient = new()
             {
-                BaseAddress = new Uri("https://api.telegram.org/bot" + Token + "/")
+                BaseAddress = new Uri("https://api.telegram.org/bot" + token + "/")
             };
 
             JsonDocument me = GetMe().Result;
@@ -85,25 +81,35 @@ public async Task<JsonDocument> GetMe()
         /// <summary>
         /// Sends a message
         /// </summary>
-        /// <param name="Text">The text of the message</param>
-        /// <param name="ChatId">The chat_id to which the message will be sent. Do not use if you want to use the chat_id from the latest update</param>
+        /// <param name="messageText">The Text of the message</param>
+        /// <param name="chatId">The chat_id to which the message will be sent. Do not use if you want to use the chat_id from the latest update</param>
+        /// <param name="replyParameters">Parameters for responding to a message</param>
+        /// <param name="keyboard">Keyboard</param>
         /// <exception cref="ArgumentNullException">It is thrown if one of the arguments is null</exception>
         /// <exception cref="Exceptions.IncorrectRequestException">It is thrown if an incorrect request was made</exception>
         /// <returns>The message that was sent</returns>
-        public async Task<Message> SendMessage(string Text, long ChatId = 0)
+        public async Task<Message> SendMessage(object messageText,
+            long? chatId = null,
+            ReplyParameters? replyParameters = null,
+            Keyboards.IKeyboard? keyboard = null)
         {
-            ArgumentNullException.ThrowIfNull(Text);
-            ArgumentNullException.ThrowIfNull(ChatId);
-
-            if (ChatId == 0)
-            {
-                ChatId = lastChatId;
-            }
+            string? text = messageText.ToString();
+            ArgumentNullException.ThrowIfNull(text);
+            chatId ??= lastChatId;
 
             Dictionary<string, string?> contentData = [];
 
-            contentData["text"] = Text.ToString();
-            contentData["chat_id"] = ChatId.ToString();
+            contentData["text"] = text.ToString();
+            contentData["chat_id"] = chatId.ToString();
+            if (replyParameters != null)
+            {
+                contentData["reply_parameters"] = JsonSerializer.Serialize(replyParameters);
+            }
+            if (keyboard != null)
+            {
+                contentData["reply_markup"] = JsonSerializer.Serialize(keyboard, keyboard.GetType());
+                Console.WriteLine(contentData["reply_markup"]);
+            }
 
             HttpContent content = new FormUrlEncodedContent(contentData);
 
@@ -172,11 +178,34 @@ public async Task StartPolling()
         public event UpdateHandler? OnUpdate;
         #endregion
 
-        #region IDisposable implementation
+        #region +, - operators
+        /// <summary>
+        /// Add the <seealso cref="OnUpdate"/> event function
+        /// </summary>
+        /// <param name="bot">Telegram bot</param>
+        /// <param name="function">Function</param>
+        /// <returns>Telegram bot</returns>
+        public static TelegramBot operator +(TelegramBot bot, UpdateHandler function)
+        {
+            bot.OnUpdate += function;
+            return bot;
+        }
+
         /// <summary>
-        /// Release the resources occupied by the bot
+        /// Remove the <seealso cref="OnUpdate"/> event function
         /// </summary>
-        /// <param name="disposing">Release managed resources</param>
+        /// <param name="bot">Telegram bot</param>
+        /// <param name="function">Function</param>
+        /// <returns>Telegram bot</returns>
+        public static TelegramBot operator -(TelegramBot bot, UpdateHandler function)
+        {
+            bot.OnUpdate -= function;
+            return bot;
+        }
+        #endregion
+
+        #region IDisposable implementation
+        /// <inheritdoc/>
         protected virtual void Dispose(bool disposing)
         {
             if (!disposedValue)
@@ -191,17 +220,13 @@ protected virtual void Dispose(bool disposing)
             }
         }
 
-        /// <summary>
-        /// Release unmanaged resources occupied by the bot
-        /// </summary>
+        /// <inheritdoc/>
         ~TelegramBot()
         {
             Dispose(disposing: false);
         }
 
-        /// <summary>
-        /// Release the resources occupied by the bot
-        /// </summary>
+        /// <inheritdoc/>
         public void Dispose()
         {
             Dispose(disposing: true);
diff --git a/Telegram bots/Tst.cs b/Telegram bots/Tst.cs
index e305c9f..7d44765 100644
--- a/Telegram bots/Tst.cs	
+++ b/Telegram bots/Tst.cs	
@@ -1,9 +1,5 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using Telegram_bots;
+using Telegram_bots;
+using Telegram_bots.Keyboards;
 
 namespace MyTGBot
 {
@@ -11,19 +7,27 @@ class Tst
     {
         public static async Task Main(string[] args)
         {
-            using TelegramBot bot = new(args[0]);
+            TelegramBot bot = new(args[0]);
 
-            bot.OnUpdate += Update;
+            bot += Update;
             await bot.StartPolling();
+
+            Console.ReadLine();
         }
 
-        public static async Task Update(Update update, TelegramBot bot)
+        private static async Task Update(Update update, TelegramBot bot)
         {
             if (update.Message != null)
             {
                 if (update.Message.Text != null)
                 {
-                    await bot.SendMessage(update.Message.Text);
+                    if (update.Message.ReplyMessage != null)
+                    {
+                        if (update.Message.ReplyMessage.Text != null)
+                        {
+                            
+                        }
+                    }
                 }
             }
         }
diff --git a/Telegram bots/Update.cs b/Telegram bots/Update.cs
index 58d8355..b6bec6a 100644
--- a/Telegram bots/Update.cs	
+++ b/Telegram bots/Update.cs	
@@ -1,4 +1,5 @@
-using System.Text.Json;
+using System.Text;
+using System.Text.Json;
 
 namespace Telegram_bots
 {
@@ -77,21 +78,19 @@ public static Update FromJSON(string jsonString)
         }
         #endregion
 
-        /// <summary>
-        /// Turns it into a string
-        /// </summary>
-        /// <returns>The line representing the update</returns>
+        /// <inheritdoc/>
         public override string ToString()
         {
-            string str = "Update id: ";
-            str += UpdateId;
+            StringBuilder builder = new();
+            builder.Append("Update id: ");
+            builder.Append(UpdateId);
             if (Message != null)
             {
-                str += ", Message: (";
-                str += Message;
-                str += ")";
+                builder.Append(", Message: (");
+                builder.Append(Message);
+                builder.Append(')');
             }
-            return str;
+            return builder.ToString();
         }
 
         /// <summary>
diff --git a/Telegram bots/User.cs b/Telegram bots/User.cs
index 8da5bb0..96c231b 100644
--- a/Telegram bots/User.cs	
+++ b/Telegram bots/User.cs	
@@ -1,4 +1,5 @@
-using System.Text.Json;
+using System.Text;
+using System.Text.Json;
 
 namespace Telegram_bots
 {
@@ -85,34 +86,32 @@ public static User FromJSON(string jsonString)
         }
         #endregion
 
-        /// <summary>
-        /// Turns it into a string
-        /// </summary>
-        /// <returns>The line representing the user</returns>
+        /// <inheritdoc/>
         public override string ToString()
         {
-            string str = "Id: ";
-            str += Id;
-            str += ", Is bot: ";
-            str += IsBot;
-            str += ", First name: ";
-            str += FirstName;
+            StringBuilder builder = new();
+            builder.Append("Id: ");
+            builder.Append(Id);
+            builder.Append(", Is bot: ");
+            builder.Append(IsBot);
+            builder.Append(", First name: ");
+            builder.Append(FirstName);
             if (LastName != null)
             {
-                str += ", Last name: ";
-                str += LastName;
+                builder.Append(", Last name: ");
+                builder.Append(LastName);
             }
             if (Username != null)
             {
-                str += ", Username: ";
-                str += Username;
+                builder.Append(", Username: ");
+                builder.Append(Username);
             }
             if (IsPremium != null)
             {
-                str += ", Is premium: ";
-                str += IsPremium;
+                builder.Append(", Is premium: ");
+                builder.Append(IsPremium);
             }
-            return str;
+            return builder.ToString();
         }
     }