Spreadsheet Document Conversion

@model AspNetCoreDemos.OfficeFileAPI.SpreadsheetDocumentConversionModel
@using DevExtreme.AspNet.Mvc

@using (Html.BeginForm("SpreadsheetConversion", "DocumentConversion", FormMethod.Post)) {
    @Html.HiddenFor(model => model.DocumentUrl)

    <div class="uploader-panel">
        @(Html.DevExtreme().FileUploader()
                           .ID("file-uploader")
                           .Name("myFile")
                           .Multiple(false)
                           .ShowFileList(true)
                           .Accept(".xlsx, .xlsm, .xlsb, .xls, .xltx, .xltm, .xlt, .xml, .csv, .txt")
                           .MaxFileSize(1048576)
                           .UploadMode(FileUploadMode.Instantly)
                           .UploadUrl(Url.Action("DocumentUpload", "SpreadsheetDocumentConversion"))
                           .OnValueChanged("fileUploader_valueChanged")
        )
    </div>
    <div class="document-downloader">
        <div class="document-downloader-item">Convert file to:</div>
        <div class="document-downloader-format-selector">
            @(Html.DevExtreme().SelectBoxFor(m => m.FileFormat)
                               .DataSource(Html.GetEnumSelectList<AspNetCoreDemos.OfficeFileAPI.SpreadsheetFileFormat>()
                               .Select(i => new { Value = int.Parse(i.Value), Text = i.Text }))
                               .ValueExpr("Value")
                               .DisplayExpr("Text")
            )
        </div>
            <div class="document-downloader-item">
                @(Html.DevExtreme().Button()
                               .ID("downloadButton")
                               .Text("Download")
                               .Disabled(true)
                               .Type(ButtonType.Default)
                               .StylingMode(ButtonStylingMode.Contained)
                               .UseSubmitBehavior(true)
                               .OnClick("DownloadClick")
            )
            </div>
            <div id="error" class="error-message-right">
                <span>@ViewBag.ErrorMessage</span>
            </div>
    </div>

    <script>
        function fileUploader_valueChanged(e) {
            var files = e.value;
            if (files.length > 0) {
                $("#selected-files .selected-item").remove();

                $.each(files, function (i, file) {
                    var $selectedItem = $("<div />").addClass("selected-item");
                    $selectedItem.append(file.name);
                    $selectedItem.appendTo($("#selected-files"));
                });

                $("#selected-files").show();

                $('#DocumentUrl').val(files[0].name);
                var button = $("#downloadButton").dxButton("instance");
                button.option("disabled", false);
            }
            else
                $("#selected-files").hide();
        }
        function DownloadClick() {
            document.getElementById("error").hidden = true;
        }
    </script>
}

using System;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Logging;

namespace AspNetCoreDemos.OfficeFileAPI {
    public partial class DocumentConversionController : DocumentProcessingController {
        public DocumentConversionController(ILogger<DocumentConversionController> logger, IWebHostEnvironment hostingEnvironment)
            : base(logger, hostingEnvironment) {
        }

        protected const string LoadDocumentExceptionString = "ERROR: Cannot convert this document.";
        protected override string SessionKey => throw new NotImplementedException();
    }
}

using System;
using System.IO;
using Microsoft.AspNetCore.Mvc;
using DevExpress.Spreadsheet;
using DevExpress.XtraPrinting;
using DevExpress.XtraSpreadsheet.Export;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Logging;

namespace AspNetCoreDemos.OfficeFileAPI {
    public class SpreadsheetDocumentConversionController : DocumentConversionController {
        public SpreadsheetDocumentConversionController(ILogger<SpreadsheetDocumentConversionController> logger, IWebHostEnvironment hostingEnvironment)
            : base(logger, hostingEnvironment) {
        }
        public static string SpreadsheetSessionKey => "SpreadsheetFileKey";
        protected override string SessionKey => SpreadsheetSessionKey;
    }

    public partial class DocumentConversionController {
        public IActionResult SpreadsheetConversion() {
            SpreadsheetDocumentConversionModel model = new SpreadsheetDocumentConversionModel();
            return View(model);
        }

        [HttpPost]
        public IActionResult SpreadsheetConversion(SpreadsheetDocumentConversionModel model) {
            Workbook workbook = new Workbook();
            byte[] data;
            try {
                if(HttpContext.Session.TryGetValue(SpreadsheetDocumentConversionController.SpreadsheetSessionKey, out data))
                    workbook.LoadDocument(data);

                MemoryStream stream = new MemoryStream();
                SpreadsheetFileFormat fileFormat = model.FileFormat;

                if(fileFormat == SpreadsheetFileFormat.Pdf) {
                    PdfExportOptions options = new PdfExportOptions();
                    options.ConvertImagesToJpeg = false;
                    workbook.ExportToPdf(stream, options);
                }
                else if(fileFormat == SpreadsheetFileFormat.Html) {
                    HtmlDocumentExporterOptions options = new HtmlDocumentExporterOptions();
                    options.EmbedImages = true;
                    options.AnchorImagesToPage = true;
                    workbook.ExportToHtml(stream, options);
                }
                else {
                    DocumentFormat format = SpreadsheetUtils.ConvertToFormat(fileFormat);
                    workbook.SaveDocument(stream, format);
                }

                string contentType = SpreadsheetUtils.ConvertToContentType(fileFormat);
                string fileExtension = SpreadsheetUtils.ConvertToFileExtension(fileFormat);
                string fileNameWithoutExtension = Path.GetFileNameWithoutExtension(Uri.UnescapeDataString(model.DocumentUrl));
                return CreateFileStreamResult(stream, contentType, fileExtension, fileNameWithoutExtension);
            } catch(Exception ex) {
                Logger.LogError(ex, LoadDocumentExceptionString);
                ViewBag.ErrorMessage = LoadDocumentExceptionString;
                return View(model);
            }
        }
    }
}

namespace AspNetCoreDemos.OfficeFileAPI {
    public class SpreadsheetDocumentConversionModel : SpreadsheetModelBase {
        public SpreadsheetDocumentConversionModel() {
            FileFormat  = SpreadsheetFileFormat.Pdf;
        }

        public string DocumentUrl { get; set; }
    }
}

namespace AspNetCoreDemos.OfficeFileAPI {
    public class SpreadsheetModelBase {
        public SpreadsheetModelBase() {
            PreviewModel = new SpreadsheetPreviewModel();
            PreviewModel.OwnerPropertyName = "PreviewModel";
            FileFormat = SpreadsheetFileFormat.Xlsx;
        }

        public SpreadsheetFileFormat FileFormat { get; set; }
        public SpreadsheetPreviewModel PreviewModel { get; internal set; }
    }
}