文件下载问题-ASP.NET MVC应用程序

Question

我在 ASP.NET MVC 应用程序的视图中有两个控制器操作和 js，用于生成和下载 Excel 文件。所有相关代码都显示在这里：

public ActionResult GetExcel()
{
    string handle = Guid.NewGuid().ToString();

    using (MemoryStream MemoryStream = new MemoryStream())
    {
        //GetExcelData returns an OfficeOpenXml.ExcelPackage object
        GetExcelData().SaveAs(MemoryStream);
        MemoryStream.Position = 0;
        TempData[handle] = MemoryStream.ToArray();
    }

    return new JsonResult()
    {
        Data = new { FileGuid = handle, FileName = "FileName" + DateTime.Now.ToString() + ".xlsx" }
    };
}

public virtual ActionResult Download(string fileGuid, string fileName)
{
    if (TempData[fileGuid] != null)
    {
        byte[] data = TempData[fileGuid] as byte[];
        return File(data, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", fileName);
    }
    else
    {
        return new EmptyResult();
    }
}

$.ajax({
  url: '@Url.Action("GetExcel", "Products")',
  type: 'POST',  
}).done(function (data) {  
  window.location = '@Url.Action("Download", "Products")' + '?fileGuid=' + data.FileGuid + '&filename=' + data.FileName;
});

我的问题是此代码会导致不一致的行为。

有时它会按预期工作，并且系统会提示我下载文件屏幕，但有时它会导致一个空白页面，其中文件的路径作为浏览器的 URL。

我注意到的一件事是，当问题发生时，浏览器网络选项卡上的文档类型是普通的，而不是application/vnd.openxmlformats-officedocument.spreadsheetml.sheet，正如预期的那样。

还有一点是，这种情况发生在应用程序位于服务器上的 IIS 上时。在开发环境中本地不会发生这种情况。

此外，显然，这似乎与文件大小无关，因为它发生在小型和大型数据集上。

Answer 1

我使用 EPPlus 库生成并下载 Excel 文件。从管理 Nuget 包安装 EPPLUS。确保您使用该库，然后在 NonCommercial LicenseContext 下使用它，如 ExcelPackage.LicenseContext = LicenseContext.NonCommercial

如果您想直接通过锚标记链接“@Url.Action("Test","Test")”生成，则使用以下代码。

 using (ExcelPackage excel = new ExcelPackage())
    {
          var stream = new MemoryStream();
          ExcelWorksheet worksheet = 
          excelPackage.Workbook.Worksheets.Add("TestWork");
        //add values in your worksheet cells you can also loop through it like  
        //worksheet.Cells[i + 2, 1].Value where i is an index starting from 0 and 1 is the column index [rowIndex,columnIndex]
         worksheet.Cells["A1"].Value = "Date";
         worksheet.Cells["A2"].Value = "10-10-2021";
        //add table styling
        int firstRow = 1;
        int lastRow = worksheet.Dimension.End.Row;
        int firstColumn = 1;
        int lastColumn = worksheet.Dimension.End.Column;
        ExcelRange rg = worksheet.Cells[firstRow, firstColumn, lastRow, lastColumn];
        string tableName = "Table1";
        ExcelTable tab = worksheet.Tables.Add(rg, tableName);
        tab.TableStyle = TableStyles.Medium2;
        excel.Save();
        byte[] bin = excelPackage.GetAsByteArray();
        Response.ClearHeaders();
        Response.Clear();
        Response.Buffer = true;
        Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
        Response.AddHeader("content-length", bin.Length.ToString());
        this.Response.AddHeader("content-disposition", string.Format("attachment;  filename={0}", YourFileName));
        Response.OutputStream.Write(bin, 0, bin.Length);
        Response.Flush();
    }

如果您发送 ajax 请求，则代码将相同，直到 excel.Save();只需更改响应的返回类型，例如 JsonResult

 var fileObject = File(excel.GetAsByteArray(), "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", "Report.xlsx");
 return new JsonResult()
                            {
                                Data = fileObject,
                                ContentType = "application/json;  charset=utf-8",
                                ContentEncoding = Encoding.UTF8,
                                JsonRequestBehavior = JsonRequestBehavior.AllowGet,
                                MaxJsonLength = Int32.MaxValue
                            };

您遇到的问题可能与文件大小有关只需尝试将响应包装在具有最大长度的 JSON 中

 return new JsonResult()
                        {
                            Data = fileObject,
                            ContentType = "application/json;  charset=utf-8",
                            ContentEncoding = Encoding.UTF8,
                            JsonRequestBehavior = JsonRequestBehavior.AllowGet,
                            MaxJsonLength = Int32.MaxValue
                        };

Ajax 请求从服务器返回的 JSONResult 响应下载文件对象在成功函数中

 $.ajax({
            type: 'POST',
            url: '',
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (response) {
                var bytes = new Uint8Array(response.FileContents);
                var blob = new Blob([bytes], { type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' });
                var downloadUrl = URL.createObjectURL(blob);
                var a = document.createElement("a");
                a.href = downloadUrl;         
                a.download = "Filename.xlsx";
                document.body.appendChild(a);
                a.click();
            },
            error: function (err) {
                alert(err);
            },
            cache: false
        });