[原]C#操作Excel-导出DataTable为excel

总结：
1.  excel中大多数类型为接口，比如 Application,  worksheet，range等，所以使用该类对象的时候一定要注意对象是否存在
2. 设置excel的单元格式为文本：range.NumberFormatLocal = "@"; 如果想设置整张表的格式为文本，可以使用以下方法：Range range = sheet.Rows; range.NumberFormatLocal = "@";
3.  excel中集合的索引一般都是从1开始。
4.  缺少参数时可以使用private object _objOpt = System.Reflection.Missing.Value;补齐。
5.  如果为web应用，一定要注意配置asp.net运行帐户对excel的COM组件的访问权限。
6.  Response.End、Response.Redirect 或 Server.Transfer 方法可能会引发ThreadAbortException异常，所以在此类方法后不应该再执行其他任务。
7.  调用Workbook.Close(true, fileName, false)方法要比Workbook.SaveAs()好。
8.  把Excel.Application赋给静态变量，理论上要比每次创建Excel.Application好，因为减少了与进程外COM组件的通信过程，但是实际体验中并没有感觉快多少，这个方式有个明显的缺点就是，如果Excel进程崩溃了，将导致RPC服务不可用，即整个导出服务都无法使用，除非重新启动web应用程序。
代码示例：
根据项目要求，写了一个可以把datatabl导出为excel的类，可以满足web、win等形式的应用程序，满足自定义列，满足excel2003以上版本。代码如下：

//--------------------------------------------
//
//             导出DataTable为Excel
//
// Author: BusyAnt(BusyAnt@qq.com)
// Blog: http://blog.busyant.cn; //       http://www.cnblogs.com/busyant // Date: 2010-04-15
// Desc: web、win；
//       自定义列
// -------------------------------------------
public class ExportExcel : IDisposable {

public enum ExcelType {
Excel2003 = 11,
Excel2007 = 12,
Excel2010 = 14
};

public enum AppType {
Web = 1,
Win = 2
};

private const int MAX_ROW_LENGTH_2003 = 65536;
private const int MAX_ROW_LENGTH_2007 = 1048576;

private const int MAX_COLUMN_LENGTH_2003 = 256;
private const int MAX_COLUMN_LENGTH_2007 = 16384;

private const string DEFAULT_SHEET_NAME = "数据表";

private const string FILE_EXTENTION_2003 = ".xls";
private const string FILE_EXTENTION_2007 = ".xlsx";

private bool _disposed = false;

private ExcelType _excelType = ExcelType.Excel2003;
private AppType _appType = AppType.Web;
private Application _app = null;
private Worksheet _currentSheet = null;
private Workbook _currentWorkbook = null;
private string _fileName = null;
private string _fileFullName = null;

private object _objOpt = System.Reflection.Missing.Value;

public ExportExcel() {
Initialize(DEFAULT_SHEET_NAME);
}

public ExportExcel(string fileName) {
if(string.IsNullOrEmpty(fileName.Trim())) {
Initialize(DEFAULT_SHEET_NAME);
} else {
Initialize(fileName);
}
}

public bool Check(System.Data.DataTable table, int[] columnList, string[] headers) {
if(null == table) {
throw new Exception("数据表为NULL");
}

if(null != columnList && null != headers) {
if(columnList.Length != headers.Length) {
throw new Exception("导出列的长度必须和表头的长度一致");
} else if(columnList.Length > table.Columns.Count || headers.Length > table.Columns.Count) {
throw new Exception("导出列的长度、表头的长度不能超过数据表的长度");
}
} else if(null == columnList && null != headers) {
if(table.Columns.Count != headers.Length) {
throw new Exception("导出列的长度必须和表头的长度一致");
} else if(headers.Length > table.Columns.Count) {
throw new Exception("表头的长度不能超过数据表的长度");
}
}
return true;
}

private int GetMaxRowCount(ExcelType excelType) {
switch(excelType) {
case ExcelType.Excel2003:
return MAX_ROW_LENGTH_2003;
case ExcelType.Excel2007:
case ExcelType.Excel2010:
return MAX_ROW_LENGTH_2007;
default:
return MAX_ROW_LENGTH_2003;
}
}

private int GetMaxColumnCount(ExcelType excelType) {
switch(excelType) {
case ExcelType.Excel2003:
return MAX_COLUMN_LENGTH_2003;
case ExcelType.Excel2007:
case ExcelType.Excel2010:
return MAX_COLUMN_LENGTH_2007;
default:
return MAX_COLUMN_LENGTH_2003;
}
}

private string GetFileFullName() {
StringBuilder fileFullName = new StringBuilder();

if(AppType.Win == _appType) {
fileFullName.Append(AppDomain.CurrentDomain.BaseDirectory).Append(_fileName);
} else {
fileFullName.Append(HttpContext.Current.Server.MapPath("~/Excel/")).Append(_fileName);
}

return fileFullName.ToString();
}

private string GetFileName(string fileName) {
StringBuilder retVal = new StringBuilder(fileName);

if(ExcelType.Excel2007 <= _excelType) {
if(AppType.Win == _appType) {
retVal.Append("_").Append(System.DateTime.Now.ToString("yyyyMMddHHmmss")).Append(FILE_EXTENTION_2007);
} else {
retVal.Append("_").Append(System.DateTime.Now.ToString("yyyyMMddHHmmss")).Append(FILE_EXTENTION_2007);
}
} else {
if(AppType.Win == _appType) {
retVal.Append("_").Append(System.DateTime.Now.ToString("yyyyMMddHHmmss")).Append(FILE_EXTENTION_2003);
} else {
retVal.Append("_").Append(System.DateTime.Now.ToString("yyyyMMddHHmmss")).Append(FILE_EXTENTION_2003);
}
}

if(retVal.Length == 0) {
throw new Exception("文件名为空");
}

return retVal.ToString();
}

private void CreateFile() {
try {
//:ATTE: 保存的是workbook，而不是application
_currentWorkbook.SaveAs(_fileFullName, _objOpt, _objOpt, _objOpt, _objOpt, _objOpt, XlSaveAsAccessMode.xlNoChange, _objOpt, _objOpt, _objOpt, _objOpt, _objOpt);

} catch {
throw new Exception("保存Excel出错");
} finally {
RemoveUnmanagedObject();
}
}

private void Export(string fileName) {

CreateFile();

if(AppType.Web == _appType) {
Export_with_Web(fileName);
} else {
Export_with_Win(fileName);
}

//Clear();  //:ATTE: 很奇怪，不会运行到此处。
}

private void Clear() {
if(File.Exists(_fileFullName)) {
File.Delete(_fileFullName);
}
}

private void CreateHeader(System.Data.DataTable table, int[] columnList, string[] headers) {
if(null != columnList) {
for(int columnIndex = 0; columnIndex < columnList.Length; columnIndex++) {
if(null != headers) {
_currentSheet.Cells[1, columnIndex + 1] = headers[columnIndex];
} else {
_currentSheet.Cells[1, columnIndex + 1] = table.Columns[columnList[columnIndex]].ColumnName;
}
}
} else {
for(int columnIndex = 0; columnIndex < table.Columns.Count; columnIndex++) {                     if(null != headers) {                         _currentSheet.Cells[1, columnIndex + 1] = headers[columnIndex];                     } else {                         _currentSheet.Cells[1, columnIndex + 1] = table.Columns[columnIndex].ColumnName;                     }                 }             }         }         private void FillData(System.Data.DataTable table, int[] columnList) {             int rowCount = GetMaxRowCount(_excelType) > table.Rows.Count ? table.Rows.Count : GetMaxRowCount(_excelType);
int columnCount = GetMaxColumnCount(_excelType) > table.Rows.Count ? table.Columns.Count : GetMaxColumnCount(_excelType);

if(null != columnList) {
for(int rowIndex = 0; rowIndex < rowCount; rowIndex++) {
for(int columnIndex = 0; columnIndex < columnList.Length; columnIndex++) {
_currentSheet.Cells[rowIndex + 2, columnIndex + 1] = table.Rows[rowIndex][columnList[columnIndex]].ToString();
}
}
} else {
for(int rowIndex = 0; rowIndex < rowCount; rowIndex++) {
for(int columnIndex = 0; columnIndex < columnCount; columnIndex++) {
_currentSheet.Cells[rowIndex + 2, columnIndex + 1] = table.Rows[rowIndex][columnIndex].ToString();
}
}
}
}

private ExcelType GetExcelType() {
ExcelType retVal;
int versionNum = Convert.ToInt32(Convert.ToSingle(_app.Version));

try {
retVal = (ExcelType)versionNum;
} catch {
throw new ApplicationException("未知Excel版本");
}
return retVal;
}

public void Initialize(string fileName) {
if(null == HttpContext.Current) {
_appType = AppType.Win;
}

_app = new ApplicationClass();

_app.Visible = false;

_excelType = GetExcelType();

_app.Workbooks.Add(true);

_currentWorkbook = _app.Workbooks[1];
_currentSheet = _app.Worksheets[1] as Worksheet;

_currentSheet.Name = fileName;
_fileName = GetFileName(fileName);
_fileFullName = GetFileFullName();

Range range = _currentSheet.Columns;
range.NumberFormatLocal = "@";
}

private void Export_with_Web(string fileName) {
FileStream fs = null;
try {
HttpResponse response = HttpContext.Current.Response;

response.Clear();
response.Buffer = true;

response.ContentType = "application/octet-stream";
response.AppendHeader("content-disposition", "attachment; filename=" + HttpContext.Current.Server.UrlPathEncode(fileName));

fs = new FileStream(_fileFullName, System.IO.FileMode.Open);
byte[] buffer = new byte[fs.Length];
fs.Read(buffer, 0, (int)fs.Length);

response.BinaryWrite(buffer);
response.End();  //:ATTE: 可能引发ThreadAbortException异常，而导致线程结束，不要在response.End()方法后再执行其他代码，否则有可能不会被执行
} catch(ThreadAbortException ex) {
string errMsg = ex.Message;
} catch(Exception ex) {
throw ex;
} finally {
fs.Close();
#if DEBUG
#else
Clear();
#endif
}

}

private void Export_with_Win(string fileName) {

}

public void Dispose() {
if(!_disposed) {
Dispose(true);
GC.SuppressFinalize(this);
}
_disposed = true;
}

private void Dispose(bool disposing) {
if(disposing) {
// managed resource
}
RemoveUnmanagedObject();
}

~ExportExcel() {
Dispose(false);
}

private void RemoveUnmanagedObject() {
if(null != _app) {
_app.Quit();  //:ATTE: Quit不一定代表进程结束，或者释放了对文件的引用。
Marshal.FinalReleaseComObject(_app);
_app = null;
}
_currentSheet = null;
_currentWorkbook = null;
}

public void Export(System.Data.DataTable table) {
this.Export(table, null, null);
}

public void Export(System.Data.DataTable table, int[] columnList) {
this.Export(table, columnList, null);
}

// index start from 0
public void Export(System.Data.DataTable table, int[] columnList, string[] headers) {
if(Check(table, columnList, headers)) {

CreateHeader(table, columnList, headers);

FillData(table, columnList);

Export(_fileName);
}
}
}

参考文章：

再现C#导出Excel源码

C#導出Excel源碼

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