Open in memory XML string as an Excel workbook without saving using windows Forms C#

Question

I have an excel string (which I built) in memory; the code looks something like this:

public static void exportToExcel()
        {
            const string startExcelXML = "<xml version>\r\n<Workbook " +
                  "xmlns=\"urn:schemas-microsoft-com:office:spreadsheet\"\r\n"
+
                  " xmlns:o=\"urn:schemas-microsoft-com:office:office\"\r\n " +
                  "xmlns:x=\"urn:schemas-    microsoft-com:office:" +
                  "excel\"\r\n xmlns:ss=\"urn:schemas-microsoft-com:"
+
                  "office:spreadsheet\">\r\n <Styles>\r\n " +
                  "<Style ss:ID=\"Default\" ss:Name=\"Normal\">\r\n " +
                  "<Alignment ss:Vertical=\"Bottom\"/>\r\n <Borders/>" +
                  "\r\n <Font/>\r\n <Interior/>\r\n <NumberFormat/>" +
                  "\r\n <Protection/>\r\n </Style>\r\n " +
                  "<Style ss:ID=\"BoldColumn\">\r\n <Font " +
                  "x:Family=\"Swiss\" ss:Bold=\"1\"/>\r\n </Style>\r\n " +
                  "<Style     ss:ID=\"StringLiteral\">\r\n <NumberFormat" +
                  " ss:Format=\"@\"/>\r\n </Style>\r\n <Style " +
                  "ss:ID=\"Decimal\">\r\n <NumberFormat/>\r\n </Style>\r\n " +
                  "<Style ss:ID=\"Integer\">\r\n <NumberFormat "
+
                  "ss:Format=\"0\"/>\r\n </Style>\r\n <Style " +
                  "ss:ID=\"DateLiteral\">\r\n <NumberFormat " +
                  "ss:Format=\"dd/mm/yyyy;@\"/>\r\n </Style>\r\n " +
                  "</Styles>\r\n ";
            const string endExcelXML = "</Workbook>";

            int sheetCount = 1;
            StringBuilder sb = new StringBuilder();

            sb.Append(startExcelXML);
            sb.Append("<Worksheet ss:Name=\"Sheet" + sheetCount + "\">");
            sb.Append("<Table>");
            sb.Append("<Row>");
            sb.Append("<Cell ss:StyleID=\"BoldColumn\"><Data ss:Type=\"String\">");
            sb.Append("Home country");
            sb.Append("</Data></Cell>");
            sb.Append("<Cell ss:StyleID=\"BoldColumn\"><Data ss:Type=\"String\">");
            sb.Append("Expatriation Type");
            sb.Append("</Data></Cell>");
            sb.Append("</Row>");
            sb.Append("<Row>");
     sb.Append("<Cell ss:StyleID=\"StringLiteral\">" +
      "<Data ss:Type=\"String\">");
     sb.Append("Singapore");
     sb.Append("</Data></Cell>");
     sb.Append("<Cell ss:StyleID=\"StringLiteral\">" +
      "<Data ss:Type=\"String\">");
     sb.Append("Benchmark");
     sb.Append("</Data></Cell>");
            sb.Append("</Row>");
            sb.Append("</Table>");
            sb.Append(" </Worksheet>");
            sb.Append(endExcelXML);
        }

I able to open the file as excel sheet only if I save the file physically; but is there any other way to just open the xml string from the memory as excel sheet?

Flanch

How are you opening it from the file system? – Abdomen

As of now we save to the physical disk and open the file using excel object. We want to avoid saving as a file to user's physical disk. – Flanch

As a VB user, I can't understand how come C# is so backwords as far as it concerns XML literals. – Bove

Answer 1

I think what you'll need is a memory mapped file implementation of some kind.

I believe, though, that .NET 4.0 will have built-in MemoryMappedFile support.

You may be able to find other .net implementations using a search engine.

Zurheide

I searched for MemoryMappedFile and got a few implementation in .net. One such impelementaion is filemap-2.0.2.zip.I am still checking on it, but on first look it looks like it is a bit complex. Is it really so complex to just open a stream using an application? – Flanch

Yes, it is pretty complex. Honestly, I don't think it is worth the effort -- it doesn't take very long to write that string out to the file system. – Zurheide

Yes; that's what I thought. We are not implementing this. Now we have changed our requirement and ask the user for the location to save the file and then save it to that location. – Flanch

Answer 2

i don't know for sure, but most Microsoft automation objects support IPersist or IPersistStream, which may let you load from a stream in memory.

Something like (pseudo-code):

xl = new Office.ExcelApplication;
(xl as IPersistStream).Load(myMemoryStream);

You can use the shell helper function CreateStreamOnHGlobal to create an IStream wrapper around some memory:

functionCreateStreamOnMemory(pData: Pointer; nCount: DWORD): IStream;
var
    hMem: HGLOBAL;
    dwError: DWORD;
    p: Pointer;
begin
    hMem := GlobalAlloc(GMEM_MOVEABLE or GMEM_NODISCARD, nCount); 
       //CreateStreamOnHGlobal says "The handle must be 
       //allocated as movable and nondiscardable."
    if hMem = 0 then
        RaiseLastWin32Error;

    p := GlobalLock(hMem);
    if p = nil then
    begin
        dwError := GetLastError;
        GlobalFree(hMem);
        raise EWin32Error.Create('Could not lock global memory object: '+SysErrorMessage(dwError));
    end;
    try
        CopyMemory(p, pData, nCount);
    finally
        GlobalUnlock(hMem);
    end;

    OleCheck(CreateStreamOnHGlobal(hMem, True, Result)); //Because we pass True, the stream will take care of freeing the HGLOBAL when the stream is released
end;

Stuff your string in the memory and see if it loads.

Staffordshire