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Miquel Coll
Asked: 2020-07-20 01:00:11 +0800 CST 2020-07-20 01:00:11 +0800 CST

Convert xls/xlsx document to html - no interop

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I have a document xlsand another xlsxalready saved in bytes[]my code and I need to pass it to html+cssso I can display it on a page.

It is important to note that I also need the cssand that means that reading each row individually from the excel is not an option since it would lose the style.

I am using Visual Studio with .NET to develop it in .

Currently it works for me from pdf that is easy to transform to html but this is not the case with xls, xlsxnor any Microsoft product since I cannot use the native library interopsince it is not a guarantee that the server has it installed.

The result would be something similar to this:

strFinalXls = strFinalXls.Replace("<body>", "<body>" + documentInfoHtml + "<BR /><BR />");

Where documentInfoHtmlis the result of transforming them bytes[]to html and strFinalXlsis simply the content that replaces that bodyof a page.

I have found a solution but practically all interopof them use either paid libraries.

Do you know any way to do it with free software or open projects?

It is also important to keep the existing CSS styles as much as possible, so answers that simply extract the content to generate it myself HTMLis not enough in the sense that it would lose all the formatting.

c#

1 Answers

  1. Best Answer

    From the NPOI library for C# (downloaded from github, NOT from the Nuget, since the Nuget is missing some DLLs):

    Main Code - Important to note that an XLS is different from an XLSX (it is marked in the code)

    Stream stream = new MemoryStream(document.Fichero); //document.Fichero son los byte[] puros del XLS/XLSX
Stream stream2 = new MemoryStream();
stream.Position = 0;
ExcelToHtmlConverter excelToHtmlConverter = new ExcelToHtmlConverter();
excelToHtmlConverter.OutputColumnHeaders = false;
excelToHtmlConverter.OutputHiddenColumns = true;
excelToHtmlConverter.OutputHiddenRows = true;
excelToHtmlConverter.OutputLeadingSpacesAsNonBreaking = false;
excelToHtmlConverter.OutputRowNumbers = true;
excelToHtmlConverter.UseDivsToSpan = true;

if (document.Extension.ToUpper() == "XLSX")
{
    //XLSX
    XSSFWorkbook workbook = new XSSFWorkbook(stream);
    excelToHtmlConverter.ProcessWorkbook(workbook);
}
else
{
    //XLS
    HSSFWorkbook workbook = new HSSFWorkbook(stream);
    excelToHtmlConverter.ProcessWorkbook(workbook);
}

excelToHtmlConverter.Document.Save(stream2);
stream2.Position = 0;
var mmmm = ReadFully(stream2);
var msAux2 = ConvertDocumentToHtmlMemoryStream(mmmm, "");
var documentInfoHtml = BytesToStringConverted(msAux2.ToArray());

    The functions ReadFully, ConvertDocumentToHtmlMemoryStreamand BytesToStringConverted:

    ReadFully - Transform a Streamto byte[]:

    public static byte[] ReadFully(Stream input)
{
    using (MemoryStream ms = new MemoryStream())
    {
        input.CopyTo(ms);
        return ms.ToArray();
    }
}

    ConvertDocumentToHtmlMemoryStream - Add information for your generation to HTML

    private MemoryStream ConvertDocumentToHtmlMemoryStream(byte[] document, string documentInfoHtml)
{
    byte[] result = null;

    //Documento
    var strBuilder = new System.Text.StringBuilder();
    foreach (var b in document)
    {
        strBuilder.Append((char)b);
    }
    var strFinalDoc = strBuilder.ToString();
    strFinalDoc = strFinalDoc.Replace("<a href=", "<br /><a href=");
    strFinalDoc = strFinalDoc.Replace("</a>", "</a><br />");

    //Información
    if (!String.IsNullOrEmpty(documentInfoHtml))
    {
        strFinalDoc = strFinalDoc.Replace("<body>", "<body>" + documentInfoHtml + "<BR /><BR />");
    }

    //Imprimir
    if (Action.ToLower() == Enumerators.ActionType.Print.ToString().ToLower())
    {
        var strImprime = "<script language='javascript' type='text/javascript'>";
        strImprime += "     window.print();";
        strImprime += "</script>";
        strImprime += "</html>";

        strFinalDoc = strFinalDoc.Replace("</html>", strImprime);
    }

    var bytes = System.Text.Encoding.Default.GetBytes(strFinalDoc);
    if (bytes.Length > 0)
    {
        return new MemoryStream(bytes);
    }
    else
    {
        return null;
    }
}

    BytesToStringConverted - Convert from byte[]tostring

    static string BytesToStringConverted(byte[] bytes)
{
    using (var stream = new MemoryStream(bytes))
    {
        using (var streamReader = new StreamReader(stream))
        {
            return streamReader.ReadToEnd();
        }
    }
}
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