Chat bot for Vkontakte on ASP.NET Core C #

This article presents a step-by-step example of creating a simple chat bot in the VK social network on ASP.NET Core C #.

Chapter 1. Preparation

Start by creating and setting up a community.

Choose any type of community

Fill in the fields with any data and ready! The group is created.

Let's get started configuring the API

Create API key (Allow all)

To respond to any events, our script needs to know about them. To do this, there are two approaches - Callback API and Long Poll. We will implement the Callback API.

Setup Callback API

Choosing the latest API version

Select the type of event "incoming message".

Useful information:

1. Introduction to the VK API
2. Callback API VK
3. JSON schema

Chapter 2. Implementing the Callback API

We start favorite IDE, we create ASP.NET Core Web Application.

Project Type: Web Api
Framework: netcoreapp 2.2

To confirm the server address, we will need to return a string with a unique value.
We take it in the settings of the Callback API.

Expand the configuration of our ASP.NET Core application .

Here we will store all the keys that will be involved in the development.

{ "Config": { "AccessToken": "0bd8573ea40badd694b4da0bbc7d54f52996", "Confirmation" : "b23557a3" }, "Logging": { "LogLevel": { "Default": "Warning" } }, "AllowedHosts": "*" } 

When an event occurs in the community, VK will send a request to the server with data in JSON format with basic information about the object that triggered the event.

 { "type":< >, "object":<,  >, "group_id":<ID ,    > } 

 { "type":"group_join", "object":{ "user_id":1, "join_type":"approved" }, "group_id":1 } 

For the convenience of deserializing incoming JSON, we use the Data Transfer Object (DTO) pattern.

 using System; using Newtonsoft.Json; namespace Cookie.Controllers { [Serializable] public class Updates { /// <summary> ///   /// </summary> [JsonProperty("type")] public string Type { get; set; } /// <summary> /// ,   ///       /// </summary> [JsonProperty("object")] public JObject Object { get; set; } /// <summary> /// ID ,     /// </summary> [JsonProperty("group_id")] public long GroupId { get; set; } } } 

To handle incoming requests, create CallbackController.cs .

 using Microsoft.AspNetCore.Mvc; using Microsoft.Extensions.Configuration; namespace Cookie.Controllers { [Route("api/[controller]")] [ApiController] public class CallbackController : ControllerBase { /// <summary> ///   /// </summary> private readonly IConfiguration _configuration; public CallbackController(IConfiguration configuration) { _configuration = configuration; } [HttpPost] public IActionResult Callback([FromBody] Updates updates) { // ,     "type" switch (updates.Type) { //       case "confirmation": //     return Ok(_configuration["Config:Confirmation"]); } //  "ok"  Callback API return Ok("ok"); } } } 

Please note: after receiving the notification, your server should return the string "ok" and HTTP status 200. If the server returns an error several times in a row, the Callback API temporarily stops sending notifications to it

Callback API is ready!

Useful information:

1. Github example
2. Serialization and deserialization of JSON data
3. DI IoC
4. SDK for .NET Core 2.2

Chapter 3. Vk?

To interact with the VK API in C #, we will use the VkNET library .

Installation via Nuget:
Package manager:
PM> Install-Package VkNet

.NET CLI:
> dotnet add package VkNet

UI:

Useful information:

1. VkNET Documentation

Chapter 4. More functionality!

Before extending the logic of the bot, let's authorize the group in our web application.
To do this, register IVkApi in the IoC container.

 using VkNet; using VkNet.Abstractions; using VkNet.Model; services.AddSingleton<IVkApi>(sp => { var api = new VkApi(); api.Authorize(new ApiAuthParams{ AccessToken = Configuration["Config:AccessToken"] }); return api; }); 

Now we will expand our controller by adding inbound processing.

We implement IVkApi

 using VkNet.Abstractions; private readonly IConfiguration _configuration; private readonly IVkApi _vkApi; public CallbackController(IVkApi vkApi, IConfiguration configuration){ _vkApi = vkApi; _configuration = configuration; } 

And the case itself, which will catch new messages. In it we add a bit of logic.

 using VkNet.Model; using VkNet.Model.RequestParams; using VkNet.Utils; case "message_new":{ //  var msg = Message.FromJson(new VkResponse(updates.Object)); //        _vkApi.Messages.Send(new MessagesSendParams{ RandomId = new DateTime().Millisecond, PeerId = msg.PeerId.Value, Message = msg.Text }); break; } 

Chapter 5. Depla

Now we need a server where all requests will be sent. One of the free options is Heroku .

After registering on the site, we will be asked to create a new application.

Enter the name of the project.

After creating the project will be redirected to the Deploy page

Heroku CLI requires Git . If you have not yet installed Git, then download it before installing the CLI.

To get started, download the Heroku CLI .

We authorize Heroku account.
$ heroku login

Go to the project directory.
$ cd ( )

Create a new directory in the current directory named .git containing all the necessary repository files - the basis of the Git repository.
$ git init

Connect to remote repository (our project)
$ heroku git:remote -a ( )

Buildpacks are responsible for converting the deployed code to slug, which can then be executed on dyno.
$ heroku buildpacks:set https://github.com/jincod/dotnetcore-buildpack.git -a ( )

To start tracking (add version control) our files.
$ git add .

$ git commit -am "cookie"

$ git push heroku master

And we go to make tea.

When our application is uploaded to Heroku, we can open it at the following link https: //**PROJECT_NAME**.herokuapp.com/

We return to our group, and in the settings of the Callback API indicate the link,
referring to the callback controller .
https: //**PROJECT_NAME**.herokuapp.com/api/callback

VK will send a JSON request to our server to confirm the address. After the response, the following notification will be displayed: Server address saved successfully

Now we will write to our bot in private messages.

Good coding!