Question

Is it possible to export a VirtualStringTree to Excel or CSV?

I am using Delphi 2007 and trying to save my VirtualStringTree data records as Excel or CSV format.

Answer 1

We have an ExcelWriter helper class, that can dump all kinds of things to Excel, e.g.

• TADOQuery
• TListView
• TVirtualStringTree

In this case the fast way (and easy to copy-paste here) is the overload that can dump a variant array into Excel:

class function TExcelWriter.ExportToExcelVariantArray(const VArray: Variant; const Title, SubTitle: WideString): Boolean;
var
    xl: OleVariant;
    workbook: OleVariant;
    worksheet: OleVariant;
    range: OleVariant;
    Rowcount, ColumnCount: Integer;
    HeaderRowIndex: Integer;
    s: WideString;
begin
    Result := False;

    if not VarIsArray(VArray) then
        raise EExcelWriterException.Create('ExportToExcelVariantArray: Supplied variant is not an array');

    if VarArrayDimCount(VArray) <> 2 then
        raise EExcelWriterException.Create('ExportToExcelEVariantArray: Supplied variant array does not have 2 dimensions ('+IntToStr(VarArrayDimCount(VArray))+')');

    ColumnCount := VarArrayHighBound(VArray, 2) - VarArrayLowBound(VArray, 2); //2 for "leftmost dimension"
    rowCount := VarArrayHighBound(VArray, 1) - VarArrayLowBound(VArray, 1); //1 for "leftmost dimension"

    try
        xl := CreateOleObject('Excel.Application');
    except
        on E:Exception do
        begin
            if (E is EOleSysError) then
            begin
                if EOleSysError(E).ErrorCode = CO_E_CLASSSTRING then
                    raise EExcelWriterException.Create('Excel is not installed.'+CRLF+
                            'Could not load "Excel.Application" object (Co_E_CLASSSTRING)')
                else
                    raise;
            end
            else
                raise;
        end;
    end;
    try
        xl.ScreenUpdating := False;
        xl.DisplayAlerts := False;  // Don't display dialogs such as "save changes to workbook".


        workbook := xl.Workbooks.Add;
        try
            Worksheet := Workbook.Worksheets[1];
            try
                Worksheet.Activate;
                Worksheet.Cells.WrapText := False;

                HeaderRowIndex := 1; //Rows&Columns in Excel start at one.
                range := TExcelWriter.GetRange(worksheet, HeaderRowIndex, 1, HeaderRowIndex+RowCount, ColumnCount);
                range.Value := VArray;

                //Bold the header row
                Worksheet.Rows[HeaderRowIndex].Font.Bold := True;
                Worksheet.Rows[HeaderRowIndex].Font.Underline := True;
                Worksheet.Columns.AutoFit;

                //Set printed header&footer
                if Copy(Title, 1, 2) = '@@' then
                    s := Copy(Title, 3, MaxInt)
                else
                    s := Title;
                if SubTitle <> '' then
                begin
                    if s <> '' then s := s+#13;
                    s := s + SubTitle;
                end;

                TExcelWriter.SetHeaderAndFooters(Worksheet,
                        s, '', '',
                        '&D &T', '', 'Page &P of &N');
            finally
                Worksheet := Unassigned;
            end;
        finally
            Workbook := Unassigned;
        end;

        //When all done
        xl.ScreenUpdating := True;
        xl.Visible := True;
        xl.UserControl := True; // Very important, prevents Excel from going
                  // away when we nil out our reference to it below.
    finally
        xl := Unassigned;
    end;

    Result := True;
end;

We have a TVirtualListView descendant of TVirtualStringTree that made it easy to transition to VirtualTrees (it has TVirtualListItem, etc). It then has a helper method ContentToVariantArray, which is similar to ContentToHtml and ContentToRtf:

function TVirtualListView.ContentToVariantArray: Variant;
var
    Columns: TColumnsArray;
    VArray: Variant;
    Node: PVirtualNode;
    ColumnCount: Integer;
    RowCount: Integer;
    nRow: Integer;
    i: Integer;
begin
    Columns := Self.Columns.GetVisibleColumns;

    ColumnCount := Length(Columns);
    RowCount := Self.Items.Count+1; //+1 for the heaader

    VArray := VarArrayCreate([0, RowCount-1, 0, ColumnCount-1], varOleStr); //Docs say cannot use varString, must be varOleStr (which is a BSTR i.e. WideString)

    nRow := 0;

    for i := 0 to ColumnCount-1 do
    begin
        VArray[nRow, i] := Self.Columns.Items[Columns[i].Index].Text;
    end;

    Node := Self.GetFirst;
    while Assigned(Node) do
    begin
        Inc(nRow);
        for i := 0 to ColumnCount-1 do
        begin
            VArray[nRow, i] := Self.Text[Node, Columns[i].Index];
        end;

        Node := Self.GetNextSibling(Node);
    end;

    Result := VArray;
end;

The main downside here is that we’re automating Excel in order to use it. This means your customer/server will need Excel installed.

The above code shows the user Excel (having to save a file to the hard drive just to look at it is wasteful), rather than creating an export file. But wouldn’t be hard to call .Save or whatever the API is.