LiveChat/Hubs/ChatHub.cs

using Microsoft.AspNetCore.SignalR;
using Microsoft.EntityFrameworkCore;

namespace LiveChat.Server.Hubs;

public class ChatHub : Hub
{
    private readonly ChattingContext _context;
    public override async Task OnConnectedAsync()
    { 
        using (var db = new ChattingContext())
        {
            var messages = db.Messages.ToList();

            messages.ForEach(Console.WriteLine);

            // Send the messages to the caller
            await Clients.Caller.SendAsync("ReceiveMessages", messages);
        }
    }

    public async Task SendMessage(string user, string message)
    {
        using (var db = new ChattingContext())
        {
            var messageData = new ChatMessage
            {
                User = user,
                Message = message,
            };
            Console.WriteLine(messageData);
            var dbSave = db.Messages.Add(messageData);
            Console.WriteLine(dbSave);
            await Clients.All.SendAsync("ReceiveMessage", user, message);
            db.SaveChanges();
        }
	}
}