C# 撸码是需要直觉的

Posted 2021-05-06 CSharp编程大全

随着撸码的时间增加，码感也会加强，今天看一个编码直觉案例吧！

案例：

需求：把查询到的数据列表生成csv文件

nuget包：CsvHelper

数据实体类：

 /// <summary> /// 商品 /// </summary> public class Goods { /// <summary> /// 编号 /// </summary> public uint ID { get; set; } /// <summary> /// 名称 /// </summary> public string Name { get; set; } /// <summary> /// 规格 /// </summary> public string Spec { get; set; } /// <summary> /// 单位 /// </summary> public string Unit { get; set; } /// <summary> /// 制造商 /// </summary> public string Manufacturer { get; set; } /// <summary> /// 价格 /// </summary> public decimal Price { get; set; }        /// <summary>        /// 这里是为了打印数据方例重写ToString()        /// </summary> public override string ToString() { return $"ID={ID},Name={Name},Unit={Unit},Spec={Spec},Price={Price},Manufacturer={Manufacturer}"; } }

定义了一个csv操作的接口：

public interface ICsvHandle{ List<Goods> ReadCsv(string file);    void WriteCsv(string file, List<Goods> goodses);}

为了演示方便，Demo中的数据列表是通过Bogus产生(bogus在之前的文章中介绍过)

 static List<Goods> GoodsCreater() { var goodses = new List<Goods>(); var options = new JsonSerializerOptions(); options.Encoder = System.Text.Encodings.Web.javascriptEncoder.Create(UnicodeRanges.All); for (var i = 0; i < 100; i++) { var goodsFaker = new Faker<Goods>("zh_CN") .RuleFor(x => x.ID, x => x.Random.UInt()) .RuleFor(x => x.Name, x => x.Random.ArrayElement( new string[] { "甲销唑注射液","葡萄糖注射液","盐水（氯化钠）","利巴韦林病毒唑针","氟康唑氯化钠注射液(康锐）","安痛定针","维生素B12针","硫酸阿米卡星注射液","氯化钠注射液（塑料瓶）","转移因子注射液","血塞通粉针","苦碟子注射液","注射用培美曲塞二钠(爱立汀)","左克注射液","维生素C注射液","硫酸庆大霉素注射液","盐酸左氧氟沙星注射液","蔗糖铁注射液","注射用青霉素钠","维生素B1针","疏血通注射液","胃复安盐酸甲氧氯普胺注射液","硫酸庆大霉素注射液","葡萄糖注射液50%","银杏达莫注射液","硫酸庆大霉素注射液","5%葡萄糖注射液","注射用氨曲南", } )) .RuleFor(x => x.Price, x => x.Random.Decimal()) .RuleFor(x => x.Unit, x => x.Random.ArrayElement(new string[] { "个", "片", "瓶", "盒", "支", "克" })) .RuleFor(x => x.Spec, x => x.Random.ArrayElement(new string[] { "5*20ml","250ml","1ml*10支","100ml:0.2g","2毫升*10支","10支","2ml*10.2克*10支","100ml","3毫升：2毫升*10支","20毫克","10mg*10支","0.5克","2ml:0.1g","0.25G*2ML","4万单位*10支","100ml*0.1g","1g","80万单位","2ml*10支","5毫克*60片","1ml:10mg","4万*2ml*10支","20ML*5支","5ml","2ml:40mg(4万单位)","250ml","0.5克*10支","5ML;17.5MG","2ML:0.5G*10支", })) .RuleFor(x => x.Manufacturer, x => x.Random.ArrayElement( new string[] { "山东齐都药业/山西云鹏","侯马霸王药业/山西晋新双鹤/天津新郑/西安/贵州","山西临汾云鹏药业、山东齐都药业/山西银湖/石家庄四药/河南科伦","安徽联谊/无锡","扬子江药业集团","新乡常乐制药/山西太原药业/天津焦作/郑州","天津药业焦作","山东方明药业集团股份有限公司","石家庄四药有限公司","湖南一格制药有限公司","哈尔滨","通化华夏制药有限责任公司","德州德药制药有限公司","扬子江药业","山西晋新双鹤药业/新乡市新辉药业/河南润弘","河南辅仁怀庆堂制药/濮阳市汇元药业/新乡常乐","广西裕源药业、四川科伦大药厂","成都天台山制药有限公司","华北制药","安阳九州药业、山东方明药业/石药银湖制药","牡丹江友博药业有限公司","濮阳汇元/天津药业集团新郑","天津药业焦作/侯马","湖南科伦/焦作民康","贵州益佰制药股份有限公司","新乡市新辉药业/新乡常乐制药/濮阳市汇元药业","山东华鲁制药/山东齐都/山西云鹏制药/西安汉丰","重庆圣华曦药业", })); goodses.Add(goodsFaker.Generate()); } return goodses; }

第一版：

csv文件格式是utf8

public class BasisCsvHandle : ICsvHandle{ public List<Goods> ReadCsv(string file) { var config = new CsvConfiguration(CultureInfo.InvariantCulture) { NewLine = "\r\n" }; using (var reader = new StreamReader(file)) using (var csv = new CsvReader(reader, config)) { var goodses = csv.GetRecords<Goods>(); return goodses.ToList(); } } public void WriteCsv(string file, List<Goods> goodses) { var config = new CsvConfiguration(CultureInfo.InvariantCulture) { NewLine = "\r\n" }; using (var writer = new StreamWriter(file)) { using (var csv = new CsvWriter(writer, config)) { csv.WriteRecords(goodses); } } }}

后来有的客户要BOM类型的UTF8，其实就是在文件开头加上 byte[] BOM = { 0xEF, 0xBB, 0xBF }; 这个字节数组就ok

为了适配合有无BOM和非BOM的UTF8，对接口进行了重构，增加默认属性(正好练一下接口默认属性的用法)，这种做法的好处是不打扰BasisCsvHandle的代码，当然，也可以更深层的重构ICsvHandle中的两个方法来适配是否是BOM UTF8

public interface ICsvHandle{ List<Goods> ReadCsv(string file);    void WriteCsv(string file, List<Goods> goodses); private static bool _isBOM; public bool IsBOM { get => _isBOM; set => _isBOM = value; }}

第二版：

public class StrengthenCsvHandle : ICsvHandle{ public List<Goods> ReadCsv(string file) { MemoryStream memory = null; using (var reader = new FileStream(file, FileMode.OpenOrCreate, FileAccess.ReadWrite)) { var bytes = new byte[reader.Length]; reader.Read(bytes, 0, bytes.Length); if (((ICsvHandle)this).IsBOM) { bytes = bytes.Skip(3).Take(bytes.Length - 3).ToArray();            } memory = new MemoryStream(bytes); } var config = new CsvConfiguration(CultureInfo.InvariantCulture) { NewLine = "\r\n" }; using (var reader = new StreamReader(memory)) using (var csv = new CsvReader(reader, config)) { var goodses = csv.GetRecords<Goods>(); return goodses.ToList(); } } public void WriteCsv(string file, List<Goods> goodses) { var config = new CsvConfiguration(CultureInfo.InvariantCulture) { NewLine = "\r\n" }; using (var writer = new StreamWriter(file)) { using (var csv = new CsvWriter(writer, config)) { csv.WriteRecords(goodses); } } if (((ICsvHandle)this).IsBOM) { //追究加BOM using (var writer = new FileStream(file, FileMode.OpenOrCreate, FileAccess.ReadWrite)) { var bytes = new byte[writer.Length]; writer.Read(bytes, 0, bytes.Length); byte[] BOM = { 0xEF, 0xBB, 0xBF }; var list = new List<byte>(); list.AddRange(BOM); list.AddRange(bytes); writer.Position = 0; writer.Write(list.ToArray(), 0, list.Count); } } }}

虽然能实现功能，但是觉得这样的代码太啰嗦，这里的本质就是在写数据时加上三个字节，读取数据时，少读三个字节，直觉告诉我，应该好像也许或者能有更简单的方式。

第三版：

public class PerfectCsvHandle : ICsvHandle{ public List<Goods> ReadCsv(string file) { var config = new CsvConfiguration(CultureInfo.InvariantCulture) { NewLine = "\r\n" }; using (var reader = new StreamReader(file)) using (var csv = new CsvReader(reader, config)) { if (((ICsvHandle)this).IsBOM) { reader.BaseStream.Position = 3; } var goodses = csv.GetRecords<Goods>(); return goodses.ToList(); }
 } public void WriteCsv(string file, List<Goods> goodses) { var config = new CsvConfiguration(CultureInfo.InvariantCulture) { NewLine = "\r\n" };
 using (var writer = new StreamWriter(file)) { using (var csv = new CsvWriter(writer, config)) { if (((ICsvHandle)this).IsBOM) { byte[] BOM = { 0xEF, 0xBB, 0xBF }; writer.Write(System.Text.Encoding.UTF8.GetString(BOM)); } csv.WriteRecords(goodses); } } }}