Question

Let’s say i have 3 byte arrays, each representin a .xls file. How can i combine them into a single xls file with 3 sheets. The SSRS reports are very rich and include charts sp oledb is not an option.

Performance is not important so i could save them to disk if needed, as a last resort i could even use an excel macro (if i knew how to do that). I tried to use microsodt.office.interop.excel but i could only manage to add a new sheet to a file, i couldn’t add an existing sheet.

Any help would be appreciated.

Answer 1

It seems to me that you just need a way to programatically write Byte arrays to a WorkBook.
Here is a method that will write a byte[] as a sheet to a specific WorkBook:

public static void WriteToSheet(string targetBookPath, byte[] fileBytes)
{
    try {
        
        object x = Type.Missing;
        
        //Create a temp file to encapsulate Byte array
        string tmpPath = IO.Path.ChangeExtension(IO.Path.GetTempFileName(), ".xls");
        My.Computer.FileSystem.WriteAllBytes(tmpPath, fileBytes, false);
        
        //Start Excel Application (COM)
        Excel.Application xlApp = new Excel.Application();
        
        //Open target book
        Excel.Workbook targetBook = xlApp.Workbooks.Open(targetBookPath, x, x, x, x, x, x, x, x, x, 
        x, x, x, x, x);
        
        //Open temp file with Excel Interop
        Excel.Workbook sourceBook = xlApp.Workbooks.Open(tmpPath, x, x, x, x, x, x, x, x, x, 
        x, x, x, x, x);
        
        //Get a reference to the desired sheet 
        Excel.Worksheet sourceSheet = (Excel.Worksheet)sourceBook.Worksheets(1);
        
        //Copy the temp sheet into WorkBook specified as "Before" parameter
        Excel.Worksheet targetBefore = (Excel.Worksheet)targetBook.Worksheets(1);
        try {
            sourceSheet.Copy(targetBefore, x);
            
            //Save and Close
            sourceBook.Close(false, x, x);
            targetBook.Close(true, x, x);
            xlApp.Workbooks.Close();
                
            xlApp.Quit();
        }
        catch (Exception ex) {
            Debug.Fail(ex.ToString);
        }
        finally {
            
            //Release COM objects
            //   Source
            DESTROY(sourceSheet);
            DESTROY(sourceBook);
            
            //   Target
            DESTROY(targetBefore);
            DESTROY(targetBook);
            
            //   App
                
            DESTROY(xlApp);
        }
        
        //Kill the temp file
            
        My.Computer.FileSystem.DeleteFile(tmpPath);
    }
    catch (Exception ex) {
        Debug.Fail(ex.ToString);
    }
}

The DESTROY method releases the COM stuff, which is pretty important:

public static void DESTROY(object o)
{
    try {
        System.Runtime.InteropServices.Marshal.ReleaseComObject(o);
    }
    catch (Exception ex) {
        Debug.Fail(ex.ToString);
        ErrorLog.Write(ex.ToString);
    }
    finally {
        o = null;
    }
}

If I understand correctly, all you would need to do is:

1. Create a new WorkBook
2. Loop through Byte arrays
3. Call WriteToSheet for each Byte array