Merge MS Word Documents in ASP.NET

_layout.cshtml

<!--drag and drop file plugin-->
<link href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-fileinput/5.0.9/css/fileinput.min.css" media="all" rel="stylesheet" type="text/css" />
<script src="https://code.jquery.com/jquery-3.3.1.min.js" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.bundle.min.js" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-fileinput/5.0.9/js/fileinput.min.js"></script>
<!--end of drag and drop-->

HomeController.cs

public FileResult UploadFiles(List<IFormFile> files, string outputFormat)
{
	if (files.Count() <= 1)
	{
		// display some message
		return null;
	}
	string fileName = "merged-document.docx";
	string path = "wwwroot/uploads";
	List<Document> documents = new List<Document>();
	// upload files 
	foreach (IFormFile file in files)
	{
		string filePath = Path.Combine(path, file.FileName);
		// Save files
		using (var stream = new FileStream(filePath, FileMode.Create))
		{
			file.CopyTo(stream);
		}
		// Add all documents to the list
		documents.Add(new Document(filePath));
	}
	// Load first Word document
	Document doc1 = documents[0];
	for (int i = 1; i < documents.Count(); i++)
	{
    // Merge Word documents
		doc1.AppendDocument(documents[i], ImportFormatMode.KeepSourceFormatting);
	}           

	var outputStream = new MemoryStream(); 
	if (outputFormat == "DOCX")
	{
		doc1.Save(outputStream, SaveFormat.Docx);
		outputStream.Position = 0;
		// Return generated Word file
		return File(outputStream, System.Net.Mime.MediaTypeNames.Application.Rtf, fileName);
	}
	else
	{
		fileName = "merged-document.pdf";
		doc1.Save(outputStream, SaveFormat.Pdf);
		outputStream.Position = 0;
		// Return generated PDF file
		return File(outputStream, System.Net.Mime.MediaTypeNames.Application.Pdf, fileName);
	}
}

index.cshtml

@{
    ViewData["Title"] = "Merge MS Word Documents in ASP.NET";
}

<div class="row">
    <div class="col-md-12" align="center">
        <h2 class="text-info">Merge Two or More Word DOC/DOCX Documents</h2>
        <p class="text-info">Merge MS Word documents and get the results in DOCX or PDF format.</p>
    </div>
</div>
<br />
<form asp-controller="Home" asp-action="UploadFiles" method="post" class="form-inline dropzone" enctype="multipart/form-data">
    <div class="row">
        <div class="col-md-12" align="center">
            <div>
                <input type="file" id="input-id" name="files" multiple accept=".doc, .docx" class="form-control file" data-preview-file-type="text" />
            </div>
        </div>
    </div>
    <hr />
    <div class="row">
        <div class="col-md-12" align="center">
            <div class="input-group-lg">
                <strong>Save As</strong>
                <select name="outputFormat" class="form-control">
                    <option value="DOCX">DOCX</option>
                    <option value="PDF">PDF</option>
                </select>
                <button type="submit" class="form-control btn btn-success">Merge and Download</button>               
            </div> 
        </div>
    </div>
</form>
<script>
    // Drag and drop plugin options
    $("#input-id").fileinput({ 'mainClass': "input-group-lg", 'showBrowse': true, 'showUpload': false, 'previewFileType': 'any', 'showClose': false, 'maxFileCount': 5, });
</script>