问提供程序选择，当尝试访问Delphi 7中的Excel表时

EN

type
  TConvertExcel = class(TAgCustomPlugin)
    ADOConnection1: TADOConnection;
    procedure FormCreate(Sender: TObject);
  private
    FSheetName: string;
    FExcelVersion: Currency;

    procedure ConnectToExcel;
    function ExcelSupported: Boolean;
    function GetExcelVersion: Currency;
  end;

var
  ConvertExcel: TConvertExcel;

implementation

uses ...

{$R *.dfm}

{
  TConvertExcel.FormCreate
  ---------------------------------------------------------------------------
}
procedure TConvertExcel.FormCreate(Sender: TObject);
begin
  FExcelVersion := GetExcelVersion;

  if ExcelSupported = False then
  begin
    grpConvertExcel.Visible := False;
    if FExcelVersion = 0 then
      lblNoExcel.Caption := 'Microsoft Excel Not Installed!'
    else
      lblNoExcel.Caption := 'Microsoft Excel Version Not Supported!';
    lblNoExcel.Caption := lblNoExcel.Caption + AsciiCRLF + AsciiCRLF +
      'Microsoft Excel 2003 or 2007 must be installed before an excel file can be converted.';
    lblNoExcel.Visible := True;
    exit;
  end;

end;

{
  TConvertExcel.GetExcelVersion
  ---------------------------------------------------------------------------
}
function TConvertExcel.GetExcelVersion: Currency;
var
  ClassID: TCLSID;
  strOLEObject: string;
  Excel: OleVariant;
begin

  result := 0;

  strOLEObject := 'Excel.Application';

  if (CLSIDFromProgID(PWideChar(WideString(strOLEObject)), ClassID) = S_OK) then
  begin
    Excel := CreateOleObject(strOLEObject);
    // qqqxxx - Should we be casting this differently?
    result := Excel.Version;
  end;

end;

{
  TConvertExcel.ExcelSupported
  ---------------------------------------------------------------------------
}
function TConvertExcel.ExcelSupported: Boolean;
begin
  result := False;
  if (FExcelVersion = 11.0) or    // Excel 2003
     (FExcelVersion = 12.0) then  // Excel 2007
    result := True;
end;

{
  TExcelConverterPreview.ConnectToExcel
  ---------------------------------------------------------------------------
}
procedure TConvertExcel.ConnectToExcel;
var
  strConn: widestring;
  SheetNameList: TStringList;
begin

/*
when connecting to Excel "database",
extended properties are used to set the Excel file version.
For an Excel95 workbook this value is "Excel 5.0" (without the quotes),
for versions Excel 97, Excel 2000, Excel 2002 or ExcelXP the value is "Excel 8.0".

IMEX=1;" tells the driver to always read the registry at
Hkey_Local_Machine/Software/Microsoft/Jet/4.0/Engines/Excel/ImportMixedTypes.
If ImportMixedTypes=Text then intermixed types will always be cast to Text.
If ImportMixedTypes=Majority Type then intermixed types will result in Null values.
Luckily Text seems to be the default.
*/

  SheetNameList := nil;

  if FExcelVersion = 11.0 then
    strConn :='Provider=Microsoft.Jet.OLEDB.4.0;' +
      'Data Source="' + txtInputFile.Text + '";' +
      'Extended Properties="Excel 8.0;HDR=No;IMEX=1"'
  else if FExcelVersion = 12.0 then
    strConn := 'Provider=Microsoft.ACE.OLEDB.12.0;' +
      'Data Source="' + txtInputFile.Text + '";' +
      'Extended Properties="Excel 12.0 Xml;HDR=No;IMEX=1"'
  else
    raise (Exception.Create(
      'The Excel Version "' + CurrToStr(FExcelVersion) +
      '" is not supported by the Excel Conversion.'));

  AdoConnection1.Connected := False;
  AdoConnection1.ConnectionString := strConn;

  try
    SheetNameList := TStringList.Create();
    try
      AdoConnection1.Open;

      ADOConnection1.GetTableNames(SheetNameList, False);
      FSheetName := SheetNameList[0];
    except
      ShowMessage('Unable to connect to Excel!' + AsciiCRLF +
                  'Make sure the Excel file ' + txtInputFile.Text + ' exists with '+
                  'sheet name ' + FSheetName + '.');
      raise;
    end;
  finally
    FreeAndNil(SheetNameList);
  end;

end;

end.