使用 CsvHelper 时转换为十进制

Question

当我尝试使用 CsvHelper 解析以下 CSV 时，我收到“无法执行转换”错误（完整错误如下）。看起来我缺少有关如何处理以小数形式读取值的内容。已经看到其他一些与设置文化有关的答案，但这似乎没有帮助。

CSV 数据为：

Title,Amount,NHS,Reference,GoCardless ID,email,surname,firstname,Full Name,DOB,Age,Right Lens,Left Lens,RightLensMonthlyAmount,LeftLensMonthlyAmount,LensMonthlyAmount,FeeMonthlyAmount,VAT Basis,LensBespokePrice,CareOnly,Notes
Mrs,24.3,N,100247,CUXXX,email@gmail.com,User,Test,Test User,17/09/1957,64,DAILIES® AquaComfort PLUS 30 Pack,DAILIES® AquaComfort PLUS 30 Pack,16.5,16.5,33,6.35,,,,

将此数据映射到属性的类是：

public class Payer
    {
        public string Title { get; set; }
        public decimal Amount { get; set; }

        [BooleanTrueValues("Y")]
        [BooleanFalseValues("N")]
        public bool NHS { get; set; }

        public string Reference { get; set; }

        [Name("GoCardless ID")]
        public string GoCardless_ID { get; set; }

        public string email { get; set; }
        public string surname { get; set; }
        public string firstname { get; set; }

        [Name("Full Name")]
        public string Fullname { get; set; }

        [Name("DOB")]
        public string Dob { get; set; }

        public int Age { get; set; }

        [Name("Right Lens")]
        public string RightLens { get; set; }
        [Name("Left Lens")]
        public string LeftLens { get; set; }

        public decimal RightLensMonthlyAmount { get; set; }
        public decimal LeftLensMonthlyAmount { get; set; }
        public decimal LensMonthlyAmount { get; set; }
        public decimal FeeMonthlyAmount { get; set; }

        [Name("VAT Basis")]
        public string VATBasis { get; set; }

        public decimal LensBespokePrice { get; set; }

        [BooleanTrueValues("Y")]
        public bool CareOnly { get; set; }

    }

我与解析 CSV 相关的代码是：

static void Main(string[] args)
    {
        var culture = new CultureInfo("en-GB");
        var config = new CsvHelper.Configuration.CsvConfiguration(culture);

        using (var reader = new StreamReader("test.csv"))
        using (var csv = new CsvReader(reader, config))
        {
            var records = csv.GetRecords<Payer>();
            Console.WriteLine("Got records"); //this prints on the console
            foreach (var payer in records)
            {
                Console.WriteLine(payer);
            }
        }
        

    }

该错误仅发生在 foreach 循环中，而不是实际的 GetRecords() 方法。

完全错误：

CsvHelper.TypeConversion.TypeConverterException: "无法执行转换。\n 文本: ''\n MemberType: System.Decimal\n TypeConverter: 'CsvHelper.TypeConversion.DecimalConverter'\nIReader 状态:\n ColumnCount: 0\ n CurrentIndex: 18\n HeaderRecord:\n["Title","Amount","NHS","Reference","GoCardless ID","email","surname","firstname","Full Name"," DOB","Age","Right Lens","Left Lens","RightLensMonthlyAmount","LeftLensMonthlyAmount","LensMonthlyAmount","FeeMonthlyAmount","增值税基础","LensBespokePrice","CareOnly","Notes"] \nIParser 状态：\n ByteCount: 0\n CharCount: 392\n Row: 2\n RawRow: 2\n Count: 21\n RawRecord:\nMrs,24.3,N,100247,CUXXX,email@gmail.com,用户,测试,测试用户,17/09/1957,64,DAILIES® AquaComfort PLUS 30 包,DAILIES® AquaComfort PLUS 30 包,16.5,16.5,33,6.35,,,,\r\n\n" 在 CsvHelper.TypeConversion.DefaultTypeConverter.ConvertFromString（字符串文本，IReaderRow 行，MemberMapData memberMapData）\n 在 CsvHelper.TypeConversion.DecimalConverter.ConvertFromString（字符串文本，IReaderRow 行，MemberMapData memberMapData）\n 在 CsvHelper.Expressions.RecordCreator.CreateT\n在 CsvHelper.Expressions.RecordManager.CreateT\n 在 CsvHelper.CsvReader.d__87`1.MoveNext()\n 在 /Users/abhi/Documents/Practice/dd-journal/ 中的 dd_journal.Program.Main(String[] args) Program.cs:22

Answer 1

所以问题在于 CSVHelper 不了解如何将 LensBespokePrice 的空字段转换为十进制值。您可以在这里使用两个选项：

1. 更新 CSV 文件以向空字段添加默认值（即 LensBespokePrice 为 0）。
2. 创建类型转换以将空单元格处理为小数。

您可以修改 CSV 文件吗？如果是这样，那么 #1 通过将 CSV 更改为（注意 LensBespokePrice 和 CareOnly 的更改）来工作：

Title,Amount,NHS,Reference,GoCardless ID,email,surname,firstname,Full Name,DOB,Age,Right Lens,Left Lens,RightLensMonthlyAmount,LeftLensMonthlyAmount,LensMonthlyAmount,FeeMonthlyAmount,VAT Basis,LensBespokePrice,CareOnly,Notes
Mrs,24.3,N,100247,CUXXX,email@gmail.com,User,Test,Test User,17/09/1957,64,DAILIES® AquaComfort PLUS 30 Pack,DAILIES® AquaComfort PLUS 30 Pack,16.5,16.5,33,6.35,,0,N,

如果没有，您将需要 type converter 用于空小数和空布尔值。例如，将所有代码放在一个文件中，可能如下所示：

using CsvHelper;
using CsvHelper.Configuration;
using CsvHelper.Configuration.Attributes;
using CsvHelper.TypeConversion;
using System;
using System.Globalization;
using System.IO;
using System.Text.Json;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            var culture = new CultureInfo("en-GB");
            var config = new CsvConfiguration(culture);
            

            using (var reader = new StreamReader("test.csv"))
            using (var csv = new CsvReader(reader, config))
            {
                var records = csv.GetRecords<Payer>();
                Console.WriteLine("Got records"); //this prints on the console
                foreach (var payer in records)
                {
                    var j = JsonSerializer.Serialize(payer);
                    Console.WriteLine(j);
                }
            }
        }
    }

    public class CustomDecimalConverter : DecimalConverter
    {
        public override object ConvertFromString(string text, IReaderRow row, MemberMapData memberMapData)
        {
            if(decimal.TryParse(text, out var result))
            {
                return result;
            } else
            {
                return decimal.Zero;
            }
        }
    }

    public class CustomBooleanConverter : BooleanConverter
    {
        public override object ConvertFromString(string text, IReaderRow row, MemberMapData memberMapData)
        {
            if (bool.TryParse(text, out var result))
            {
                return result;
            }
            else
            {
                return false;
            }
        }
    }

    public class Payer
    {
        public string Title { get; set; }
        public decimal Amount { get; set; }

        [BooleanTrueValues("Y")]
        [BooleanFalseValues("N")]
        public bool NHS { get; set; }

        public string Reference { get; set; }

        [Name("GoCardless ID")]
        public string GoCardless_ID { get; set; }

        public string email { get; set; }
        public string surname { get; set; }
        public string firstname { get; set; }

        [Name("Full Name")]
        public string Fullname { get; set; }

        [Name("DOB")]
        public string Dob { get; set; }

        public int Age { get; set; }

        [Name("Right Lens")]
        public string RightLens { get; set; }
        [Name("Left Lens")]
        public string LeftLens { get; set; }

        public decimal RightLensMonthlyAmount { get; set; }
        public decimal LeftLensMonthlyAmount { get; set; }
        public decimal LensMonthlyAmount { get; set; }
        public decimal FeeMonthlyAmount { get; set; }

        [Name("VAT Basis")]
        public string VATBasis { get; set; }

        [TypeConverter(typeof(CustomDecimalConverter))]
        public decimal LensBespokePrice { get; set; }

        [BooleanTrueValues("Y")]
        [BooleanFalseValues("N")]
        [TypeConverter(typeof(CustomBooleanConverter))]
        public bool CareOnly { get; set; }

    }
}

请注意，我在Main 方法内的foreach 循环中添加了JsonSerializer.Serialize(payer);，以便您可以从控制台查看JSON 结果。

我添加了两个自定义转换器（CustomBooleanConverter 和 CustomDecimalConverter）。然后更新payer 类以将属性添加到LensBespokePrice 和CareOnly 属性。此外，CareOnly 上没有用于 false 值的属性，虽然不是必需的，但这是一种很好的做法。

澄清为什么这只发生在您的foreach 循环而不是var records = csv.GetRecords<Payer>(); 是因为在枚举记录之前这些值实际上并未转换为您的payer 类。

Answer 2

Payer 是一整类值。当您写入控制台时，它似乎正在尝试转换。我相信您需要告诉它您想要打印的付款人的哪一部分：

Console.WriteLine(payer.surname);