using System;
using System.Collections.Generic;
using System.Data;
using System.Text;public static class DataTableHelper
{public static string DataTableToFileContent(this DataTable datatable, string seperator = ",", bool inchuleColumnName = true, string defaultNullColumnValue = "", bool trimColumValue = true){/*https://stackoverflow.com/a/28503521 */if (defaultNullColumnValue == null){throw new NullReferenceException("'defaultNullColumnValue' should not be null");}StringBuilder sb = new StringBuilder();/*header*/if (inchuleColumnName){for (int i = 0; i < datatable.Columns.Count; i++){sb.Append(datatable.Columns[i]);if (i < datatable.Columns.Count - 1){sb.Append(seperator);}}sb.AppendLine();}/*data*/long lineNo = 0;string value;foreach (DataRow row in datatable.Rows){lineNo++;if (lineNo > 1){sb.AppendLine();}for (int i = 0; i < datatable.Columns.Count; i++){var columnValue = row[i];value = columnValue == DBNull.Value ? defaultNullColumnValue : columnValue.ToString();if (trimColumValue){value = value.Trim();}sb.Append(value);if (i < datatable.Columns.Count - 1){sb.Append(seperator);}}}return sb.ToString();}
}

创建Excel文件对象的扩展方法

using OfficeOpenXml;
using System;
using System.Collections.Generic;
using System.Data;
using System.Text;public static class DataTableHelper
{private static string GetExcelColumnName(int columnNumber){/*1 equal Ahttps://stackoverflow.com/questions/181596/how-to-convert-a-column-number-e-g-127-into-an-excel-column-e-g-aa*/int dividend = columnNumber;string columnName = String.Empty;int modulo;while (dividend > 0){modulo = (dividend - 1) % 26;columnName = Convert.ToChar(65 + modulo).ToString() + columnName;dividend = (int)((dividend - modulo) / 26);}return columnName;}public static ExcelPackage DataTableToExcel(this DataTable datatable, string sheetName = "Sheet1",  bool inchuleColumnName = true, string defaultNullColumnValue = null, bool trimColumValue = true){if (String.IsNullOrEmpty(sheetName)){throw new NullReferenceException("'sheetName' should not be null or empty");}sheetName = sheetName.Trim();ExcelPackage excel = new ExcelPackage();var workSheet = excel.Workbook.Worksheets.Add(sheetName);int columnCount = datatable.Columns.Count;int lineNo = 1;/*header*/if (inchuleColumnName){int headerNumber = 1;foreach (DataColumn column in datatable.Columns){workSheet.Cells[lineNo, headerNumber].Value = column.ColumnName;headerNumber++;}workSheet.Row(lineNo).Style.Font.Bold = true;/*add filter to header*/workSheet.Cells[String.Format("{0}{1}:{2}{3}", GetExcelColumnName(1), lineNo, GetExcelColumnName(columnCount), lineNo)].AutoFilter = true;lineNo++;}/*data*/string value;foreach (DataRow row in datatable.Rows){for (int i = 0; i < columnCount; i++){var columnValue = row[i];value = columnValue == DBNull.Value ? defaultNullColumnValue : columnValue.ToString();if (trimColumValue && value != null){value = value.Trim();}int columnNo = i + 1;/*https://stackoverflow.com/a/36824090*/workSheet.Cells[lineNo, columnNo].Value = string.IsNullOrEmpty(value) ? null : value;}lineNo++;}for (int i = 1; i <= columnCount; i++){workSheet.Column(i).AutoFit();}return excel;}
}

让我们将代码添加到我们现有的扩展帮助类中。

using System.IO;public class FileSystemHelper
{/// <summary>/// string p1 = "c:\\temp\\";/// string p2 = "\\subdir\\file\\";/// to c:\temp\subdir\file/// </summary>public static string CombineDirectory(string rootDirectoryPath, string childDirectoryPath){rootDirectoryPath = rootDirectoryPath.TrimEnd('\\');childDirectoryPath = childDirectoryPath.Trim('\\');return Path.Combine(rootDirectoryPath, childDirectoryPath);}/// <summary>/// string p1 = "c:\\temp\\";/// string p2 = "\\file.txt";/// to c:\temp\file.txt/// </summary>public static string CombineFile(string rootDirectoryPath, string filePathOrName){rootDirectoryPath = rootDirectoryPath.TrimEnd('\\');filePathOrName = filePathOrName.Trim('\\');return Path.Combine(rootDirectoryPath, filePathOrName);}public static void CreateDirectoryIfNotExists(string directoryPath){if (!DirectoryExists(directoryPath)){Directory.CreateDirectory(directoryPath);}}public static void DeleteFileIfExists(string filePath){if (FileExists(filePath)){File.Delete(filePath);}}public static bool DirectoryExists(string directoryPath){return Directory.Exists(directoryPath);}public static bool FileExists(string filePath){return File.Exists(filePath);}/*file*/public static void MoveFile(string fromFilePath, string toFilePath){File.Move(fromFilePath, toFilePath);}public static void WriteAllText(string filePath, string contents){/*create file if doesn't exist*/File.WriteAllText(filePath, contents);}
}

其他方法也很有用，因此也请看一看。

string filePath = @"c:\dataTable.csv";
DataTable dataTable = Data.Instance.DataTable;FileSystemHelper.DeleteFileIfExists(filePath);
FileSystemHelper.WriteAllText(filePath, dataTable.DataTableToFileContent());

要使用其他扩展名（如txt），我们只需将文件名更改为“dataTable.txt ”。

string filePath = @"c:\dataTable.xlsx";
DataTable dataTable = Data.Instance.DataTable;FileSystemHelper.DeleteFileIfExists(filePath);
using (var excel = dataTable.DataTableToExcel())
{excel.SaveAs(new FileInfo(filePath));
}

我相信XLS也可以，只需更改扩展名并尝试一下即可。