ML.NET 预测纽约出租车票价 - 程序不包含适合入口点的静态 'Main' 方法

Question

我试图做 ML.net 的例子来预测纽约的出租车票价，但是当我完成教程时有消息：程序不包含适合入口点的静态'Main'方法

这是我做的代码：

Class Program.cs

using System;
using System.IO;
using Microsoft.ML;
using Microsoft.ML.Data;
using Microsoft.ML.Models;
using Microsoft.ML.Trainers;
using Microsoft.ML.Transforms;
using System.Threading.Tasks;

namespace TaxiFarePrediction2
{
    public class Program
    {
        static readonly string _datapath = Path.Combine(Environment.CurrentDirectory, "Data", "taxi-fare-train.csv");
        static readonly string _testdatapath = Path.Combine(Environment.CurrentDirectory, "Data", "taxi-fare-test.csv");
        static readonly string _modelpath = Path.Combine(Environment.CurrentDirectory, "Data", "Model.zip");


        static async Task Main(string[] args)
        {
            PredictionModel<TaxiTrip, TaxiTripFarePrediction> model = await Train();
            Evaluate(model);
            TaxiTripFarePrediction prediction = model.Predict(TestTrips.Trip1);
            Console.WriteLine("Predicted fare: {0}, actual fare: 29.5", prediction.FareAmount);
        }


        public static async Task<PredictionModel<TaxiTrip, TaxiTripFarePrediction>> Train()
        {
            var pipeline = new LearningPipeline
            {
                new TextLoader(_datapath).CreateFrom<TaxiTrip>(useHeader: true, separator: ','),
                new ColumnCopier(("FareAmount", "Label")),
                new CategoricalOneHotVectorizer(
                    "VendorId",
                    "RateCode",
                    "PaymentType"),
                new ColumnConcatenator(
                    "Features",
                    "VendorId",
                    "RateCode",
                    "PassengerCount",
                    "TripDistance",
                    "PaymentType"),
                new FastTreeRegressor()
            };
            PredictionModel<TaxiTrip, TaxiTripFarePrediction> model = pipeline.Train<TaxiTrip, TaxiTripFarePrediction>();
            await model.WriteAsync(_modelpath);
            return model;
        }

        private static void Evaluate(PredictionModel<TaxiTrip, TaxiTripFarePrediction> model)
        {
            var testData = new TextLoader(_testdatapath).CreateFrom<TaxiTrip>(useHeader: true, separator: ',');
            var evaluator = new RegressionEvaluator();
            RegressionMetrics metrics = evaluator.Evaluate(model, testData);
            Console.WriteLine($"Rms = {metrics.Rms}");
            Console.WriteLine($"RSquared = {metrics.RSquared}");
        }


    }
}

class TaxiTrip.cs

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.ML.Runtime.Api;

namespace TaxiFarePrediction2
{
    public class TaxiTrip
    {
        [Column("0")]
        public string VendorId;

        [Column("1")]
        public string RateCode;

        [Column("2")]
        public float PassengerCount;

        [Column("3")]
        public float TripTime;

        [Column("4")]
        public float TripDistance;

        [Column("5")]
        public string PaymentType;

        [Column("6")]
        public float FareAmount;
    }

    public class TaxiTripFarePrediction
    {
        [ColumnName("Score")]
        public float FareAmount;
    }
}

class TestTrips.cs

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.ML.Runtime.Api;

namespace TaxiFarePrediction2
{
    public class TaxiTrip
    {
        [Column("0")]
        public string VendorId;

        [Column("1")]
        public string RateCode;

        [Column("2")]
        public float PassengerCount;

        [Column("3")]
        public float TripTime;

        [Column("4")]
        public float TripDistance;

        [Column("5")]
        public string PaymentType;

        [Column("6")]
        public float FareAmount;
    }

    public class TaxiTripFarePrediction
    {
        [ColumnName("Score")]
        public float FareAmount;
    }
}

教程位于：https://docs.microsoft.com/en-us/dotnet/machine-learning/tutorials/taxi-fare

请帮我做这个例子。

Answer 1

C# 7.1之前的Main方法不支持asycn，如果你使用的是早期版本，你可以启动一次main，然后在main方法中创建可以异步的任务。

你可以写一些Chris Moschini

提到的东西

class Program
{
static void Main(string[] args)
{
    Task.Run(async () =>
    {
        // Do any async anything you need here without worry
    }).GetAwaiter().GetResult();
}

您发布的 link 清楚地提到了指定的 c# 版本...

Because the async Main method is the feature added in C# 7.1 and the default language version of the project is C# 7.0, you need to change the language vers ion to C# 7.1 or higher. To do that, right-click the project node in Solution Explorer and select Properties. Select the Build tab and select the Advanced button. In the dropdown, select C# 7.1 (or a higher version). Select the OK button.

A good read on main with async

ML.NET 预测纽约出租车票价 - 程序不包含适合入口点的静态 'Main' 方法

ML.NET to predict New York taxi fares - Program does not contain a static 'Main' method suitable for an entry point

c#

ml.net