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撸码是需要直觉的
发布时间：2023/12/4
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豆豆
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：
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)
第一版：
csv文件格式是utf8
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BOMusing (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);}}} }总结
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