【C#プログラム入門 レベル2】ポンコツ2人組がWPFでMQTTメッセージを受信するプログラムに挑戦してみました！

<Window x:Class="WpfMqttReceiver.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d"
        Title="MQTT Receiver" Height="350" Width="525"
        Closing="Window_Closing">
    <Grid>
        <StackPanel>
            <TextBlock Text="Received Messages:" FontWeight="Bold" Margin="10"/>
            <TextBox x:Name="ReceiveTextBox" TextWrapping="Wrap" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto" IsReadOnly="True" Height="200" Margin="10"/>
        </StackPanel>
    </Grid>
</Window>

using System.Runtime.Serialization;

[DataContract]
public class ReceiveData
{
    [DataMember(Name = "message")]
    public string Message { get; set; }
}

using System;
using System.IO;
using System.Runtime.Serialization.Json;
using System.Text;
using System.Windows;
using uPLibrary.Networking.M2Mqtt;
using uPLibrary.Networking.M2Mqtt.Messages;

namespace WpfMqttReceiver
{
    public partial class MainWindow : Window
    {
        private MqttClient mqttClient;

        public MainWindow()
        {
            InitializeComponent();

            // MQTT Broker の接続情報を設定
            string brokerAddress = "localhost"; // MQTTブローカーのアドレス
            mqttClient = new MqttClient(brokerAddress);

            // MQTT メッセージを受信したときのイベントハンドラを設定
            mqttClient.MqttMsgPublishReceived += MqttClientOnMqttMsgPublishReceived;

            // 接続
            string clientId = Guid.NewGuid().ToString();
            mqttClient.Connect(clientId);

            // トピックをサブスクライブ
            string topic = "test/topic"; // 受信したいトピック
            mqttClient.Subscribe(new string[] { topic }, new byte[] { MqttMsgBase.QOS_LEVEL_EXACTLY_ONCE });
        }

        private void MqttClientOnMqttMsgPublishReceived(object sender, MqttMsgPublishEventArgs e)
        {
            // メッセージを受信したときの処理
            string jsonMessage = Encoding.UTF8.GetString(e.Message);

            // JSONデシリアライズ
            ReceiveData receiveData;
            using (MemoryStream stream = new MemoryStream(Encoding.UTF8.GetBytes(jsonMessage)))
            {
                DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(ReceiveData));
                receiveData = (ReceiveData)serializer.ReadObject(stream);
            }

            // UIに表示
            Dispatcher.Invoke(() => { ReceiveTextBox.Text += $"Received Message: {receiveData.Message}\n"; });
        }

        private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
        {
            // アプリケーションが終了するときに MQTT ブローカーとの接続を切断
            if (mqttClient.IsConnected)
            {
                mqttClient.Disconnect();
            }
        }
    }
}