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ChatClient

@page "/"

<ChatClient />

namespace BlazorFiddleProject
{
    using Microsoft.AspNetCore.Components.Builder;
    using Microsoft.Extensions.DependencyInjection;

    using System;
    using System.Collections.Generic;
    using System.Linq;

    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddSingleton<MessageService>();
            services.AddScoped<UserMessageService>();
        }

        public void Configure(IComponentsApplicationBuilder app)
        {
            app.AddComponent<App>("app");
        }
    }

    public class ChatMessage
    {
        public List<int> RecipientIds { get; private set; }
        public string Message { get; private set; }
        public int CreatedBy { get; private set; }
        public DateTime Created { get; private set; }

        private ChatMessage() { }

        public ChatMessage(int createdBy, List<int> recipientIds, string message)
        {
            CreatedBy = createdBy;
            RecipientIds = recipientIds;
            Message = message;
            Created = DateTime.Now;
        }
    }

    public class MessageService
    {
        public List<ChatMessage> Messages { get; set; } = new List<ChatMessage>();

        public void SendMessage(ChatMessage chatMessage)
        {
            //Add message to message store

            Messages.Add(chatMessage);
        }
    }

    public class UserMessageService // Inject as scoped service
    {
        MessageService MessageService { get; set; }

        public int UserID { get; set; }
        DateTime LastCheck = DateTime.MinValue;

        public List<ChatMessage> UserMessages { get; set; } = new List<ChatMessage>();

        public UserMessageService(MessageService messageService) => MessageService = messageService;

        public void SetUserId(int userId)
        {
            UserID = userId;
        }

        public void GetUserMessages()
        {
            if (UserID == 0)
                throw new ArgumentNullException(nameof(UserID), "A user ID has not been set for the user message service.");

            var messages = MessageService.Messages.Where(m =>
                (
                    m.RecipientIds?.Contains(UserID) == true
                    || m.RecipientIds == null
                    || m.CreatedBy == UserID
                )
                && m.Created > LastCheck)
                ?.ToList();

            if (messages?.Any() == true)
            {
                LastCheck = messages.Max(m => m.Created);

                UserMessages = UserMessages.Concat(messages).OrderBy(m => m.Created).ToList();
            }
        }
    }
}

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8"/>
    <meta name="viewport" content="width=device-width">
    <title>BlazorFiddleProject</title>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
	
	<script src="_content/MatBlazor/dist/matBlazor.js"></script>

    <style>
        div[MessageContainer] {
            border: 2px solid #CCC;
            width: 50vw;
            border-radius: 0.3em;
        }
        div[MessageContainer] div[Message][NotMessage] {
            text-align: center;
        }
        div[MessageContainer] div[Message]:not([NotMessage]) {
            padding: 1em;
            margin: 1em;
            background-color: #CCC;
            border-radius: 0.3em;
            margin-right: 5em;
        }
        div[MessageContainer] div[Message]:not([NotMessage])[IsUser] {
            background-color: darkgreen;
            color: #FFF;
            margin-right: 1em;
            margin-left: 5em;
        }
        div[MessageContainer] div[Message]:not([NotMessage]) span[Details] {
            font-size: 0.7em;
            opacity: 0.7;
        }

    </style>

    <script type="text/javascript">
    </script>
</head>
<body>
<app>Loading...</app>

<script src="_framework/blazor.webassembly.js"></script>
<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
</body>
</html>

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