var contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";是什么意思

这是一个变量声明语句，声明了一个名为contentType的变量，其值为"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"。这个值是一种MIME类型，用于指定文件的内容类型，具体来说，这个类型是用于表示Excel电子表格文件的。

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response.setHeader("Content-Disposition", "attachment;fileName=" + URLEncoder.encode("roi-export.xlsx", "utf8")); response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");//application/vnd.openxmlformats-officedocument.spreadsheetml.sheet response.setCharacterEncoding("utf-8"); xssfWorkbook.write(response.getOutputStream()); xssfWorkbook.close();

这段代码是用于在服务器端生成一个Excel文件，并将其作为附件下载到客户端。具体的实现方式是通过设置`Content-Disposition`响应头来指定下载文件的文件名，通过设置`ContentType`响应头来指定下载文件的MIME类型，最后将Excel文件的内容写入响应输出流中即可。这段代码中使用了`org.apache.poi.xssf.usermodel.XSSFWorkbook`类来创建Excel文件，并调用`write`方法将其写入响应输出流中。

public ActionResult ExportToExcel() { var package = new ExcelPackage();//是一个epplus中的类 var worksheet = package.Workbook.Worksheets.Add("Sheet1");//Workbook 是 Excel 工作簿，Worksheets 是工作簿中的工作表集合 // 添加表头 cell代表表格或单元格 worksheet.Cells[1, 1].Value = "姓名"; worksheet.Cells[1, 2].Value = "年龄"; worksheet.Cells[1, 3].Value = "性别"; // 添加数据 worksheet.Cells[2, 1].Value = "张三"; worksheet.Cells[2, 2].Value = 20; worksheet.Cells[2, 3].Value = "男"; worksheet.Cells[3, 1].Value = "李四"; worksheet.Cells[3, 2].Value = 25; worksheet.Cells[3, 3].Value = "女"; // 自适应列宽 worksheet.Cells.AutoFitColumns(); // 导出 Excel 文件 var fileStream = new MemoryStream(package.GetAsByteArray()); var fileName = "export.xlsx"; var contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"; return View(new FileViewModel { FileStream = fileStream, ContentType = contentType, FileName = fileName }); }@model该怎么写

您可以这样写：

public class FileViewModel
{
public MemoryStream FileStream { get; set; }
public string ContentType { get; set; }
public string FileName { get; set; }
}

public ActionResult ExportToExcel()
{
var package = new ExcelPackage();
var worksheet = package.Workbook.Worksheets.Add("Sheet1");

worksheet.Cells[1, 1].Value = "姓名";
worksheet.Cells[1, 2].Value = "年龄";
worksheet.Cells[1, 3].Value = "性别";

worksheet.Cells[2, 1].Value = "张三";
worksheet.Cells[2, 2].Value = 20;
worksheet.Cells[2, 3].Value = "男";

worksheet.Cells[3, 1].Value = "李四";
worksheet.Cells[3, 2].Value = 25;
worksheet.Cells[3, 3].Value = "女";

worksheet.Cells.AutoFitColumns();

var fileStream = new MemoryStream(package.GetAsByteArray());
var fileName = "export.xlsx";
var contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";

return View(new FileViewModel { FileStream = fileStream, ContentType = contentType, FileName = fileName });
}