Question

我创建了一个Microsoft .Net Core 2.1控制台应用程序。这是我的代码

using System;
using Microsoft.Azure.EventHubs;
using System.Threading.Tasks;
using System.Threading;
using System.Text;
using System.Collections.Generic;

namespace bog_cs_AzureIoTMessageReader
{
    class Program
    {
        private readonly static string s_eventHubsCompatibleEndpoint = "sb://foobar.servicebus.windows.net/";
        private readonly static string s_eventHubsCompatiblePath = "...";
        private readonly static string s_iotHubSasKey = "secret";
        private readonly static string s_iotHubSasKeyName = "secret";
        private static EventHubClient s_eventHubClient;

        private static async Task ReceiveMessagesFromDeviceAsync(string partition, CancellationToken ct)
        {
            // Create the receiver using the default consumer group.
            // For the purposes of this sample, read only messages sent since 
            // the time the receiver is created. Typically, you don't want to skip any messages.
            var eventHubReceiver = s_eventHubClient.CreateReceiver("$Default", partition, EventPosition.FromEnqueuedTime(DateTime.Now));
            Console.WriteLine("Create receiver on partition: " + partition);
            while (true)
            {
                if (ct.IsCancellationRequested) break;
                Console.WriteLine("Listening for messages on: " + partition);
                // Check for EventData - this methods times out if there is nothing to retrieve.
                var events = await eventHubReceiver.ReceiveAsync(100);

                // If there is data in the batch, process it.
                if (events == null) continue;

                foreach (EventData eventData in events)
                {
                    string data = Encoding.UTF8.GetString(eventData.Body.Array);
                    Console.WriteLine("Message received on partition {0}:", partition);
                    Console.WriteLine("  {0}:", data);
                    Console.WriteLine("Application properties (set by device):");
                    foreach (var prop in eventData.Properties)
                    {
                        Console.WriteLine("  {0}: {1}", prop.Key, prop.Value);
                    }
                    Console.WriteLine("System properties (set by IoT Hub):");
                    foreach (var prop in eventData.SystemProperties)
                    {
                        Console.WriteLine("  {0}: {1}", prop.Key, prop.Value);
                    }
                }
            }
        }


        static async Task Main(string[] args)
        {
            Console.WriteLine("IoT Hub Quickstarts - Read device to cloud messages. Ctrl-C to exit.\n");

            // Create an EventHubClient instance to connect to the
            // IoT Hub Event Hubs-compatible endpoint.
            var connectionString = new EventHubsConnectionStringBuilder(new Uri(s_eventHubsCompatibleEndpoint), s_eventHubsCompatiblePath, s_iotHubSasKeyName, s_iotHubSasKey);
            s_eventHubClient = EventHubClient.CreateFromConnectionString(connectionString.ToString());

            // Create a PartitionReciever for each partition on the hub.
            var runtimeInfo = await s_eventHubClient.GetRuntimeInformationAsync();
            var d2cPartitions = runtimeInfo.PartitionIds;

            CancellationTokenSource cts = new CancellationTokenSource();

            Console.CancelKeyPress += (s, e) =>
            {
                e.Cancel = true;
                cts.Cancel();
                Console.WriteLine("Exiting...");
            };

            var tasks = new List<Task>();
            foreach (string partition in d2cPartitions)
            {
                tasks.Add(ReceiveMessagesFromDeviceAsync(partition, cts.Token));
            }

            // Wait for all the PartitionReceivers to finsih.
            Task.WaitAll(tasks.ToArray());

        }
    }
}

执行此操作时，我收到错误消息

1> ------开始构建：项目：bog-cs-AzureIoTMessageReader，配置：调试任何CPU ------ 1> Program.cs（55,22,55,26）：错误 CS8107：功能'异步主要'在C＃7.0中不可用。请用语言版本7.1或更高版本。 1> CSC：错误CS5001：程序执行不包含适用于入口点的静态“ Main”方法1> Done 建筑项目“ bog-cs-AzureIoTMessageReader.csproj”-失败。 ===========构建：0成功，1失败，0最新，跳过0 ==========

这是怎么了？我该如何解决？

Answer 1

您必须将项目的LangVersion设置为至少7.1

<Project Sdk="Microsoft.NET.Sdk.Web">
 ...
  <PropertyGroup>
    <LangVersion>7.1</LangVersion>
  </PropertyGroup>
 ...
</Project>

错误CS5001：程序不包含适用于.Net Core Console App中的入口点的静态“ Main”方法

1 个答案: