This is a .Net Core Single Page Chat Application using React as the Client App which uses SignalR. The backend serves a Websocket end-point using SignalR and some basic Web API end-points to fetch initial data. Online users are tracked using a Redis Distributed Cache and the Chat messages are persisted in Azure Table Storage.

• UsersController

  • CheckIfUserExist Used to Check if the user already exists with the name at the time of Registration.
  • URL : /api/Users/exists?name
  • Method : GET
  • Auth required : NO
  • LoggedOnUsers Fetches the List of Online users from Redis Cache using UserTracker.
  • URL : /api/Users/LoggedOnUsers
  • Method : GET
  • Auth required : NO

• ChatController

  • InitialMessages Fetches Top 100 messages from the Storage Table.
  • URL : /api/Chat/InitialMessages
  • Method : GET
  • Auth required : NO

ChatHub.cs is derived from the abstract class Hub.cs present in Microsoft.AspNetCore.SignalR. In this class methods can be implementede which are invoked from the Client App.

• AddMessage(string username, string message) - This method adds the message to the Storage Table and then invokes the method 'MessageAdded' to all the Clients to update the UI.

• UserConnected(string username) - This methods adds the user to the Online user list in the cache and invokes the 'UserLoggedOn' method to all the Clients.

  Other Methods invoked from the backend to the Clients include UserLoggedOn and UserLoggedOff which are invoked on new user connected and when users leaves respectively.

ChatService uses and instance of ChatRepository which is injected in the class as a dependency. The purpose of the ChatRepository class is just to Add or Get messages from the Azure Table Storage, whereas, ChatService itself acts as a wrapper on the repository. This way if we are to use a new Storage type e.g. SQL, we can just create a new repository and inject it in the ChatService

ChatMessageTableEntity.cs is a model class derived from TableEntity, which is the base class to store entites in the Azure Table Storage.

ChatService and ChatRepository implemts interfaces IChatService and IChatRepository which makes it easier to used with Dependency Injection.

UserTracker is similar to ChatService and is used to Add users to the Online List in Redis and Get the online users list from the cache. This class implements IUserTracker

The project uses the DI pattern and injects dependencies in constructors, which is provided by Microsoft.Extensions.DependencyInjection, and is also used to achieve IoC between classes and their dependencies.

The app is deployed to Azure Web App using Azure DevOps Build pipeline. App Url: https://rafay-chatapp-spa-01.azurewebsites.net/