MQTTNet 4.1.6.1152版本出现命名空间错误求助

阿华AIGC实验室

2026-6-14

问题解决：MQTTNet 4.x命名空间错误

你遇到的错误是因为MQTTNet 4.x版本对命名空间做了重构，原来的MQTTnet.Client.Options和MQTTnet.Client.Subscribing子命名空间已被移除，相关类型全部合并到MQTTnet.Client主命名空间下。

解决步骤：

删除代码中这两行多余的using引用：

using MQTTnet.Client.Options;
using MQTTnet.Client.Subscribing;

保留using MQTTnet.Client;即可，MqttClientOptionsBuilder、MqttClientSubscribeOptionsBuilder等类型现在都属于这个命名空间。

修改后的完整代码：

using System;
using System.Text;
using System.Threading.Tasks;
using MQTTnet;
using MQTTnet.Client;

namespace OTtoIT
{
    class Program
    {
        static async Task Main(string[] args)
        {
            string brokerAddress = "0.0.0.0";  // Your MQTT broker IP address
            int brokerPort = 1883;  // Default MQTT port
            string topic = "#";  // Your MQTT topic

            // Create a new MQTT client
            var mqttClient = new MqttFactory().CreateMqttClient();

            // Create client options using the MqttClientOptionsBuilder
            var mqttClientOptions = new MqttClientOptionsBuilder()
                .WithClientId("YourClientId")
                .WithTcpServer(brokerAddress, brokerPort)
                .WithCleanSession()
                .Build();

            // Set up the handler for receiving messages
            mqttClient.ApplicationMessageReceivedAsync += e =>
            {
                var payload = Encoding.UTF8.GetString(e.ApplicationMessage.PayloadSegment.ToArray());
                Console.WriteLine($"Received message: {payload}");
                return Task.CompletedTask;
            };

            // Connect to the MQTT broker
            await mqttClient.ConnectAsync(mqttClientOptions);
            Console.WriteLine("Connected to the broker.");

            // Subscribe to the topic
            var subscribeOptions = new MqttClientSubscribeOptionsBuilder()
                .WithTopicFilter(f => { f.WithTopic(topic); })
                .Build();

            await mqttClient.SubscribeAsync(subscribeOptions);
            Console.WriteLine($"Subscribed to topic: {topic}");

            // Keep the application running to receive messages
            Console.WriteLine("Press any key to exit...");
            Console.ReadKey();

            // Disconnect the client
            await mqttClient.DisconnectAsync();
            Console.WriteLine("Disconnected from the broker.");
        }
    }
}