Word (RTF) Document Conversion

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

@using (Html.BeginForm("WordRTFConversion", "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(".rtf, .doc, .docx, .txt, .mht, .odt, .xml, .epub, .htm, .html")
                           .MaxFileSize(1048576)
                           .UploadMode(FileUploadMode.Instantly)
                           .UploadUrl(Url.Action("DocumentUpload", "RichEditDocumentConversion"))
                           .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.RichEditFileFormat>()
                               .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 Microsoft.AspNetCore.Hosting;
using System;

namespace AspNetCoreDemos.OfficeFileAPI {
    public partial class DocumentConversionController : DocumentProcessingController {
        public DocumentConversionController(IWebHostEnvironment hostingEnvironment)
            : base(hostingEnvironment) {
        }

        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.XtraRichEdit;
using Microsoft.AspNetCore.Hosting;

namespace AspNetCoreDemos.OfficeFileAPI {
    public class RichEditDocumentConversionController : DocumentConversionController {
        public RichEditDocumentConversionController(IWebHostEnvironment hostingEnvironment)
            : base(hostingEnvironment) {
        }

        public static string RichEditSessionKey => "RichEditFileKey";
        protected override string SessionKey => RichEditSessionKey;
    }

    public partial class DocumentConversionController {
        public IActionResult WordRTFConversion() {
            WordRTFDocumentConversionModel model = new WordRTFDocumentConversionModel();
            return View(model);
        }

        [HttpPost]
        public IActionResult WordRTFConversion(WordRTFDocumentConversionModel model) {
            RichEditDocumentServer documentServer = new RichEditDocumentServer();
            byte[] data;
            try {
                if (HttpContext.Session.TryGetValue(RichEditDocumentConversionController.RichEditSessionKey, out data))
                    documentServer.LoadDocument(data);

                MemoryStream stream = new MemoryStream();
                RichEditFileFormat documentType = model.FileFormat;
                DocumentFormat format = WordRTFUtils.ConvertToFormat(documentType);
                if(format == DocumentFormat.Undefined)
                    documentServer.ExportToPdf(stream);
                else
                    documentServer.SaveDocument(stream, format);

                string contentType = WordRTFUtils.ConvertToContentType(documentType);
                string fileExtension = WordRTFUtils.ConvertToFileExtension(documentType);
                string fileNameWithoutExtension = Path.GetFileNameWithoutExtension(Uri.UnescapeDataString(model.DocumentUrl));
                return CreateFileStreamResult(stream, contentType, fileExtension, fileNameWithoutExtension);
            } catch {
                ViewBag.ErrorMessage = LoadDocumentExceptionString;
                return View(model);
            }
        }
    }
}

namespace AspNetCoreDemos.OfficeFileAPI {
    public class WordRTFDocumentConversionModel : WordRTFModelBase {
        public WordRTFDocumentConversionModel() {
            FileFormat = RichEditFileFormat.Pdf;
        }

        public string DocumentUrl { get; set; }
    }
}

namespace AspNetCoreDemos.OfficeFileAPI {
    public class WordRTFModelBase {
        public WordRTFModelBase() {
            PreviewModel = new WordRTFPreviewModel();
            PreviewModel.OwnerPropertyName = "PreviewModel";
            FileFormat = RichEditFileFormat.Rtf;
        }

        public RichEditFileFormat FileFormat { get; set; }
        public WordRTFPreviewModel PreviewModel { get; internal set; }
    }

    public class WordRTFPreviewModel {
        public WordRTFPreviewModel() {
        }

        public string OwnerPropertyName { get; set; }
        public string PreviewDocumentAction { get; set; }
        public string ControllerName { get; set; }
        public int IFrameSize { get; set; } = 452;
    }
}