我有一个 Asp.Net Mvc 应用程序。在此应用程序中，我具有将数据从数据库下载到 Excel 文件的功能（使用 OpenXml Sdk）。现在可以了。但是当数据很大时，从用户请求到响应下载窗口的时间变成了 10+ 分钟。这是因为两个漫长的过程：
- 从 MSSQL 服务器获取数据。
- 在服务器的内存中生成 Excel 文档。（只有在 Excel 文档完成后才开始下载）
第一个问题是通过使用 DataReader 解决的。现在 excel 文件的生成在用户请求进入网络服务器后开始。
为了解决第二个问题，我们需要在 HttpResponse.OutputStream 上生成 Excel 文档，但是这个流不是 Seekable 并且在开始之前生成失败。
有谁知道任何可以帮助解决此问题的解决方法？
我的生成函数示例：
public void GenerateSpreadSheetToStream(IDataReader dataReader, Stream outputStream)
{
var columnCaptions = FillColumnCaptionsFromDataReader(dataReader.GetSchemaTable());
//fails on next line with exception "Cannot open package because FileMode or FileAccess value is not valid for the stream."
using (var spreadsheetDocument = SpreadsheetDocument.Create(outputStream, SpreadsheetDocumentType.Workbook))
{
spreadsheetDocument.AddWorkbookPart();
var workSheetPart = spreadsheetDocument.WorkbookPart.AddNewPart<WorksheetPart>();
OpenXmlWriter writer;
using (writer = OpenXmlWriter.Create(workSheetPart))
{
using (writer.Write(new Worksheet()))
{
using (writer.Write(new SheetData()))
{
using (writer.Write(w =>
w.WriteStartElement(new Row(), new[] {new OpenXmlAttribute("r", null, 1.ToString(CultureInfo.InvariantCulture))})))
{
var cells =
columnCaptions.Select(caption => new Cell()
{
CellValue = new CellValue(caption.Item2),
DataType = CellValues.String
});
foreach (var cell in cells)
{
writer.WriteElement(cell);
}
}
var i = 2;
while (dataReader.Read())
{
var oxa = new[] { new OpenXmlAttribute("r", null, i.ToString(CultureInfo.InvariantCulture)) };
using (writer.Write(w => w.WriteStartElement(new Row(), oxa)))
{
var cells =
columnCaptions.Select(
(c, j) =>
new Cell
{
CellValue = new CellValue(dataReader[c.Item1].ToString()),
DataType = CellValues.String,
CellReference = new StringValue(GetSymbolByCellNumber(j))
});
foreach (var cell in cells)
{
writer.WriteElement(cell);
}
}
i++;
}
}
}
}
using (writer = OpenXmlWriter.Create(spreadsheetDocument.WorkbookPart))
{
using (writer.Write(new Workbook()))
{
using (writer.Write(new Sheets()))
{
var sheet = new Sheet
{
Id = spreadsheetDocument.WorkbookPart.GetIdOfPart(workSheetPart),
SheetId = 1,
Name = SheetName
};
writer.WriteElement(sheet);
}
}
}
}
}
private static string GetSymbolByCellNumber(int number)
{
var r = number/26;
var s = (char) ((number%26) + 65);
return new string(s, r);
}
我的 FileStreamResultWithTransformation（用于使用 HttpResponse.OutputStream）：
public class FileStreamResultWithTransformation : FileResult
{
private readonly Action<Stream> _action;
public FileStreamResultWithTransformation(Action<Stream> action, string contentType, string fileName) : base(contentType)
{
_action = action;
FileDownloadName = fileName;
}
protected override void WriteFile(HttpResponseBase response)
{
response.BufferOutput = false;
_action(response.OutputStream); ->> it fails there
}
}
堆栈跟踪：
[IOException：无法打开包，因为 FileMode 或 FileAccess 值对流无效。]
System.IO.Packaging.Package.ValidateModeAndAccess(Stream s, FileMode mode, FileAccess access) +784533
System.IO.Packaging.Package.Open( Stream stream, FileMode packageMode, FileAccess packageAccess, Boolean streaming) +89
System.IO.Packaging.Package.Open(Stream stream, FileMode packageMode, FileAccess packageAccess) +10
DocumentFormat.OpenXml.Packaging.OpenXmlPackage.CreateCore(Stream stream) +192
DocumentFormat.OpenXml.Packaging.SpreadsheetDocument.Create（流流，SpreadsheetDocumentType 类型，布尔自动保存）+215
DocumentFormat.OpenXml.Packaging.SpreadsheetDocument.Create（流流，SpreadsheetDocumentType 类型）+44
--------.GenerateSpreadSheetToStream(IDataReader dataReader, Stream outputStream) 在 d:\Work\Epsilon\development\Web\trunk\Sources\Epsilon.DocumentGenerator\XlsXGenerator.cs:119