How to generate and display Excel files in thumbnail view

<style>
    table ul li {
        float: left;
        margin-right: 30px;
        padding: 5px;
        border: 3px solid transparent;
    }
 
        table ul li:hover {
            border-color: #c8e277;
        }
 
    table a:hover {
        text-decoration: none;
    }
</style>
<h3>Server File Directory:</h3>
<table cellpadding="10">
    <tr>
        <td>
            Select file to open:
        </td>
    <tr>
    <tr>
        <td>
            <ul style="list-style: none;margin: 0; padding: 0;">
                @foreach (var file in (List<string>)@ViewBag.Filenames)
                {
                    var thumbnailImg = "/ExcelFiles/Thumbnails/" + Path.GetFileNameWithoutExtension(file) + ".png";
                    <li>
                        <a href='@Url.Action("ExcelView", "Home", new { fileName = file })'>
                            <div style="width:200px; height: 100px; overflow: hidden;">
                                <img src=@thumbnailImg />
                            </div>
                            <br />
                            @file
                        </a>
                    </li>
                }
            </ul>
        </td>
    </tr>
</table>

<h4>View excel(@ViewBag.fileName) in Spreadsheet</h4>
<div class="control" style="height: 600px;">
    @(Html.EJ().Spreadsheet<object>("Spreadsheet")
        .ShowRibbon(false)
        .AllowFormulaBar(false)
        .ImportSettings(import => 
            import.ImportMapper("Import").ImportUrl((string)ViewBag.fileName)
        )
    )
</div>

public ActionResult Index()
{
    ViewBag.Filenames = GetFilenames();
    RefreshThumbnail();
    return View();
}
public ActionResult ExcelView(string fileName)
{
    ViewBag.fileName = fileName;
    return View();
}
private void RefreshThumbnail()
{
    var destinationPath = Server.MapPath("~/ExcelFiles");
    string[] filePaths = Directory.GetFiles(destinationPath);
 
    for (int i = 0; i < filePaths.Length; i++)
    {
        var filePath = filePaths[i];
 
        ExcelEngine excelEngine = new ExcelEngine();                
        IApplication application = excelEngine.Excel;
        IWorkbook workbook = application.Workbooks.Open(filePath);
 
        IWorksheet worksheet = workbook.Worksheets[0];                
        Image image = worksheet.ConvertToImage(1, 1, worksheet.UsedRange.LastRow + 1, worksheet.UsedRange.LastColumn + 1, ImageType.Bitmap, null);
        image.Save(destinationPath + "\\Thumbnails\\" + Path.GetFileNameWithoutExtension(filePath) + ".png", ImageFormat.Png);
 
        //Close the workbook.
        workbook.Close();
        excelEngine.Dispose();
 
    }
}
private List<string> GetFilenames()
{
    List<string> fileNames = new List<string>();
    var destinationPath = Server.MapPath("~/ExcelFiles");
    string[] filePaths = Directory.GetFiles(destinationPath);
 
    for (int i = 0; i < filePaths.Length; i++)
        fileNames.Add(Path.GetFileName(filePaths[i]));
 
    return fileNames;
}
 
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Import(ImportRequest importRequest)
{
    if (String.IsNullOrEmpty(importRequest.Url))
        return importRequest.SpreadsheetActions();
    else
    {
        Stream fileStream = System.IO.File.Open(Server.MapPath("~/ExcelFiles/") + importRequest.Url, FileMode.Open, FileAccess.Read);
        importRequest.FileStream = fileStream;
        importRequest.Url = null;
        importRequest.FileStream.Position = 0;
        string spreadsheetData = Spreadsheet.Open(importRequest);
        fileStream.Close();
        return Content(spreadsheetData);
    }
}