C#_.net core 3.0自定义读取.csv文件数据_解决首行不是标题的问题_Linqtocsv改进
linqtocsv文件有不太好的地方就是：无法设置标题的行数，默认首行就是标题，这不是很尴尬吗？ 并不是所有的csv文件严格写的首行是标题，下面全是数据，我接受的任务就是读取很多.csv报表数据，里面就有很多前几行是说明性内容，下面才是标题和数据。为了更好的解决这个问题，自己写吧...
本博客没有照搬linqtocsv全部源码，保留了主要功能，并对其优化，为我所用，哈哈...
下面是主要代码：
1-主文件CsvHelper：
这里在独自解析数据的时候，遇到了很多坑：
a-遇到数据含有分隔符的问题的解决办法，代码已经包含了
b-遇到了解析源文档数据时，未指定字符编码时，部分数据丢失导致csv文件个别行数据解析异常的问题，针对该问题，就是老老实实把读取文件时加了字符编码的参数进去，默认UTF-8。
using Microsoft.Extensions.Logging;using PaymentAccountAPI.Helper;using System;using System.Collections.Generic;using System.IO;using System.Linq;using System.Reflection;using System.Text;namespace PaymentAccountAPI.CSV{ public class CsvHelper { /// <summary> /// 日志 /// </summary> private ILogger _Logger { get; set; } public CsvHelper(ILogger<CsvHelper> logger) { this._Logger = logger; } public List<T> Read<T>(string filePath, CsvFileDescription fileDescription) where T : class, new() { List<T> tList = new List<T>(50 * 10000); T t = null; int currentRawIndex = 0; if (File.Exists(filePath)) { using (StreamReader streamReader = new StreamReader(filePath, fileDescription.Encoding)) { Dictionary<int, FieldMapper> fieldMapperDic = FieldMapper.GetModelFieldMapper<T>().ToDictionary(m => m.CSVTitleIndex); string rawValue = null; string[] rawValueArray = null; PropertyInfo propertyInfo = null; string propertyValue = null; bool rawReadEnd = false; bool isExistSplitChart = false; do { rawValue = streamReader.ReadLine(); //标题行 if (currentRawIndex > fileDescription.TitleRawIndex) { if (!string.IsNullOrEmpty(rawValue)) { //替换字符串含有分隔符为{分隔符}，最后再替换回来 if (rawValue.Contains("\"")) { isExistSplitChart = true; int yhBeginIndex = 0; int yhEndIndex = 0; string yhText = null; do { yhBeginIndex = StringHelper.GetIndexOfStr(rawValue, "\"", 1); yhEndIndex = StringHelper.GetIndexOfStr(rawValue, "\"", 2); yhText = rawValue.Substring(yhBeginIndex, (yhEndIndex - yhBeginIndex + 1)); string newYHText = yhText.Replace("\"", "").Replace(fileDescription.SeparatorChar.ToString(), "{分隔符}"); rawValue = rawValue.Replace(yhText, newYHText); } while (rawValue.Contains("\"")); } rawValueArray = rawValue.Split(fileDescription.SeparatorChar); t = new T(); foreach (var fieldMapper in fieldMapperDic) { propertyInfo = fieldMapper.Value.PropertyInfo; propertyValue = rawValueArray[fieldMapper.Key - 1]; if (!string.IsNullOrEmpty(propertyValue)) { try { if (isExistSplitChart && propertyValue.Contains("{分隔符}")) { propertyValue = propertyValue.Replace("{分隔符}", fileDescription.SeparatorChar.ToString()); } TypeHelper.SetPropertyValue(t, propertyInfo.Name, propertyValue); } catch (Exception e) { this._Logger.LogWarning(e, $"第{currentRawIndex + 1}行数据{propertyValue}转换属性{propertyInfo.Name}-{propertyInfo.PropertyType.Name}失败！"); continue; } } } tList.Add(t); } else { rawReadEnd = true; } } currentRawIndex++; } while (rawReadEnd == false); } } return tList; } public void WriteFile<T>(string path, List<T> tList, CsvFileDescription fileDescription) where T : class, new() { if (!string.IsNullOrEmpty(path)) { string fileDirectoryPath = null; if (path.Contains("\\")) { fileDirectoryPath = path.Substring(0, path.LastIndexOf('\\')); } else { fileDirectoryPath = path.Substring(0, path.LastIndexOf('/')); } if (!Directory.Exists(fileDirectoryPath)) { Directory.CreateDirectory(fileDirectoryPath); } int dataCount = tList.Count; Dictionary<int, FieldMapper> fieldMapperDic = FieldMapper.GetModelFieldMapper<T>().ToDictionary(m => m.CSVTitleIndex); int titleCount = fieldMapperDic.Keys.Max(); string[] rawValueArray = new string[titleCount]; StringBuilder rawValueBuilder = new StringBuilder(); string rawValue = null; T t = null; PropertyInfo propertyInfo = null; int currentRawIndex = 0; int tIndex = 0; using (StreamWriter streamWriter = new StreamWriter(path, false, fileDescription.Encoding)) { do { try { rawValue = "";#if DEBUG if (currentRawIndex % 10000 == 0) { this._Logger.LogInformation($"已写入文件：{path}，数据量：{currentRawIndex}"); }#endif if (currentRawIndex >= fileDescription.TitleRawIndex) { //清空数组数据 for (int i = 0; i < titleCount; i++) { rawValueArray[i] = ""; } if (currentRawIndex > fileDescription.TitleRawIndex) { t = tList[tIndex]; tIndex++; } foreach (var fieldMapperItem in fieldMapperDic) { //写入标题行 if (currentRawIndex == fileDescription.TitleRawIndex) { rawValueArray[fieldMapperItem.Key - 1] = fieldMapperItem.Value.CSVTitle; } //真正的数据从标题行下一行开始写 else { propertyInfo = fieldMapperItem.Value.PropertyInfo; object propertyValue = propertyInfo.GetValue(t); string formatValue = null; if (propertyValue != null) { if (propertyInfo.PropertyType is IFormattable && !string.IsNullOrEmpty(fieldMapperItem.Value.OutputFormat)) { formatValue = ((IFormattable)propertyValue).ToString(fieldMapperItem.Value.OutputFormat, null); } else { formatValue = propertyValue.ToString(); } //如果属性值含有分隔符，则使用双引号包裹 if (formatValue.Contains(fileDescription.SeparatorChar.ToString())) { formatValue = $"\"{formatValue}\""; } rawValueArray[fieldMapperItem.Key - 1] = formatValue; } } } rawValue = string.Join(fileDescription.SeparatorChar, rawValueArray); } rawValueBuilder.Append(rawValue + "\r\n"); } catch (Exception e) { this._Logger.LogWarning(e, $"(异常)Excel第{currentRawIndex+1}行，数据列表第{tIndex + 1}个数据写入失败！rawValue：{rawValue}"); throw; } currentRawIndex++; } while (tIndex < dataCount); streamWriter.Write(rawValueBuilder.ToString()); streamWriter.Close(); streamWriter.Dispose(); } } } }}
2-CSV映射类特性：
using System;namespace PaymentAccountAPI.CSV{ /// <summary> /// Csv文件类特性标记 /// </summary> [System.AttributeUsage(System.AttributeTargets.Field | System.AttributeTargets.Property, AllowMultiple = false)] public class CsvColumnAttribute : System.Attribute { internal const int defaultTitleIndex = Int32.MaxValue; /// <summary> /// 标题 /// </summary> public string Title { get; set; } /// <summary> /// 标题位置（从0开始） /// </summary> public int TitleIndex { get; set; } /// <summary> /// 字符输出格式（数字和日期类型需要） /// </summary> public string OutputFormat { get; set; } public CsvColumnAttribute() { Title = ""; TitleIndex = defaultTitleIndex; OutputFormat = ""; } public CsvColumnAttribute(string title, int titleIndex, string outputFormat) { Title = title; TitleIndex = titleIndex; OutputFormat = outputFormat; } }}
3-CSV文件描述信息类：
using System.Text;namespace PaymentAccountAPI.CSV{ public class CsvFileDescription { public CsvFileDescription() : this(0) { } public CsvFileDescription(int titleRawIndex) : this(',', titleRawIndex, Encoding.UTF8) { } public CsvFileDescription(char separatorChar, int titleRawIndex, Encoding encoding) { this.SeparatorChar = separatorChar; this.TitleRawIndex = titleRawIndex; this.Encoding = encoding; } /// <summary> /// CSV文件字符编码 /// </summary> public Encoding Encoding { get; set; } /// <summary> /// 分隔符（默认为（,）,也可以是其他分隔符如(\t)） /// </summary> public char SeparatorChar { get; set; } /// <summary> /// 标题所在行位置（默认为0，没有标题填-1） /// </summary> public int TitleRawIndex { get; set; } }}
4-映射类获取关系帮助类：
using System.Collections.Generic;using System.Linq;using System.Reflection;namespace PaymentAccountAPI.CSV{ /// <summary> /// 字段映射类 /// </summary> public class FieldMapper { /// <summary> /// 属性信息 /// </summary> public PropertyInfo PropertyInfo { get; set; } /// <summary> /// 标题 /// </summary> public string CSVTitle { get; set; } /// <summary> /// 标题下标位置 /// </summary> public int CSVTitleIndex { get; set; } /// <summary> /// 字符输出格式（数字和日期类型需要） /// </summary> public string OutputFormat { get; set; } public static List<FieldMapper> GetModelFieldMapper<T>() { List<FieldMapper> fieldMapperList = new List<FieldMapper>(100); List<PropertyInfo> tPropertyInfoList = typeof(T).GetProperties().ToList(); CsvColumnAttribute csvColumnAttribute = null; foreach (var tPropertyInfo in tPropertyInfoList) { csvColumnAttribute = (CsvColumnAttribute)tPropertyInfo.GetCustomAttribute(typeof(CsvColumnAttribute)); if (csvColumnAttribute != null) { fieldMapperList.Add(new FieldMapper { PropertyInfo = tPropertyInfo, CSVTitle = csvColumnAttribute.Title, CSVTitleIndex = csvColumnAttribute.TitleIndex, OutputFormat = csvColumnAttribute.OutputFormat }); } } return fieldMapperList; } }}
5-其他扩展类：
namespace PaymentAccountAPI.Helper{ public class StringHelper { /// <summary> /// 获取字符串中第strPosition个位置的str的下标 /// </summary> /// <param name="text"></param> /// <param name="str"></param> /// <param name="strPosition"></param> /// <returns></returns> public static int GetIndexOfStr(string text, string str, int strPosition) { int strIndex = -1; int currentPosition = 0; if (!string.IsNullOrEmpty(text) && !string.IsNullOrEmpty(str) && strPosition >= 1) { do { currentPosition++; if (strIndex == -1) { strIndex = text.IndexOf(str); } else { strIndex = text.IndexOf(str, strIndex + 1); } } while (currentPosition < strPosition); } return strIndex; } }}
最后就是将CsvHelper注入到单例中，就可以使用了...
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