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csharp-code-csv文件解析

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using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;

class CsvUtil
{
    /// <summary>
    /// 将CSV数据转换为DataTable
    /// </summary>
    /// <param name="csvFilePath">csv文件路径</param>
    /// <param name="isRowHead">是否将第一行作为字段名</param>
    /// <returns></returns>
    public static DataTable ToDataTable2(string csvFilePath, bool isRowHead)
    {
        DataTable dt = null;
        if (File.Exists(csvFilePath))
        {
            string csvstr = File.ReadAllText(csvFilePath, Encoding.Default);
            if (!string.IsNullOrEmpty(csvstr))
            {
                dt = ToDataTable(csvstr, isRowHead);
            }
        }
        return dt;
    }
    /// <summary>
    /// 将CSV数据转换为DataTable
    /// </summary>
    /// <param name="csv">包含以","分隔的CSV数据的字符串</param>
    /// <param name="isRowHead">是否将第一行作为字段名</param>
    /// <returns></returns>
    public static DataTable ToDataTable(string csv, bool isRowHead)
    {
        DataTable dt = null;
        if (!string.IsNullOrEmpty(csv))
        {
            dt = new DataTable();
            string[] csvRows = csv.Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);
            string[] csvColumns = null;
            if (csvRows != null)
            {
                if (csvRows.Length > 0)
                {
                    //第一行作为字段名,添加第一行记录并删除csvRows中的第一行数据
                    if (isRowHead)
                    {
                        csvColumns = FromCsvLine(csvRows[0]);
                        csvRows[0] = null;
                        for (int i = 0; i < csvColumns.Length; i++)
                        {
                            dt.Columns.Add(csvColumns[i]);
                        }
                    }
                    for (int i = 0; i < csvRows.Length; i++)
                    {
                        if (csvRows[i] != null)
                        {
                            csvColumns = FromCsvLine(csvRows[i]);
                            //检查列数是否足够,不足则补充
                            if (dt.Columns.Count < csvColumns.Length)
                            {
                                int columnCount = csvColumns.Length - dt.Columns.Count;
                                for (int c = 0; c < columnCount; c++)
                                {
                                    dt.Columns.Add();
                                }
                            }
                            dt.Rows.Add(csvColumns);
                        }
                    }
                }
            }
        }
        return dt;
    }
    /// <summary>
    /// 解析一行CSV数据
    /// </summary>
    /// <param name="csv">csv数据行</param>
    /// <returns></returns>
    public static string[] FromCsvLine(string csv)
    {
        List<string> csvLiAsc = new List<string>();
        List<string> csvLiDesc = new List<string>();
        if (!string.IsNullOrEmpty(csv))
        {
            //顺序超找
            int lastIndex = 0;
            int quotCount = 0;
            //剩余的字符串
            string lstr = string.Empty;
            for (int i = 0; i < csv.Length; i++)
            {
                if (csv[i] == '"')
                {
                    quotCount++;
                }
                else if (csv[i] == ',' && quotCount % 2 == 0)
                {
                    csvLiAsc.Add(ReplaceQuote(csv.Substring(lastIndex, i - lastIndex)));
                    lastIndex = i + 1;
                }
                if (i == csv.Length - 1 && lastIndex < csv.Length)
                {
                    lstr = csv.Substring(lastIndex, i - lastIndex + 1);
                }
            }
            if (!string.IsNullOrEmpty(lstr))
            {
                //倒序超找
                lastIndex = 0;
                quotCount = 0;
                string revStr = Reverse(lstr);
                for (int i = 0; i < revStr.Length; i++)
                {
                    if (revStr[i] == '"')
                    {
                        quotCount++;
                    }
                    else if (revStr[i] == ',' && quotCount % 2 == 0)
                    {
                        csvLiDesc.Add(ReplaceQuote(Reverse(revStr.Substring(lastIndex, i - lastIndex))));
                        lastIndex = i + 1;
                    }
                    if (i == revStr.Length - 1 && lastIndex < revStr.Length)
                    {
                        csvLiDesc.Add(ReplaceQuote(Reverse(revStr.Substring(lastIndex, i - lastIndex + 1))));
                        lastIndex = i + 1;
                    }
                }
                string[] tmpStrs = csvLiDesc.ToArray();
                Array.Reverse(tmpStrs);
                csvLiAsc.AddRange(tmpStrs);
            }
        }
        return csvLiAsc.ToArray();
    }
    /// <summary>
    /// 反转字符串
    /// </summary>
    /// <param name="str"></param>
    /// <returns></returns>
    private static string Reverse(string str)
    {
        string revStr = string.Empty;
        foreach (char chr in str)
        {
            revStr = chr.ToString() + revStr;
        }
        return revStr;
    }
    /// <summary>
    /// 替换CSV中的双引号转义符为正常双引号,并去掉左右双引号
    /// </summary>
    /// <param name="csvValue">csv格式的数据</param>
    /// <returns></returns>
    private static string ReplaceQuote(string csvValue)
    {
        string rtnStr = csvValue;
        if (!string.IsNullOrEmpty(csvValue))
        {
            //首尾都是"
            Match m = Regex.Match(csvValue, "^\"(.*?)\"$");
            if (m.Success)
            {
                rtnStr = m.Result("${1}").Replace("\"\"", "\"");
            }
            else
            {
                rtnStr = rtnStr.Replace("\"\"", "\"");
            }
        }
        return rtnStr;
    }
}