Delphi function to check a string if it's number

function IsNumber(Text: String): Boolean;

var i: Integer;

    c: char;

begin

  Result := True;

  if Length(Text) <= 0 then

    Result := False;

  for i := 1 to Length(Text) do

  begin

    c := Text[i];

    if not ((c >= '0') and (c <= '9')) then

    if not ((c = DecimalSeparator) and (i > 1)) then

    if not ((c = '-') and (i = 1)) then

    if not ((c = '+') and (i = 1)) then

    begin

      Result := False;

      //Break;

    end;

  end;

end;

Extract integer part of a string - Delphi function

function ExtractIntegerPartOfString(const AValue: String; var StrPart: String; var IntPart: Integer): String;

var

  I: Integer;

begin

  Result := '0';

  StrPart := '';

  IntPart := 1;

  for I := length(AValue)-1 downto 0 do

  begin

    if not (Ord(AValue[I]) in [Ord('0')..Ord('9')]) then

    begin

      if Length(AValue)-I > 0 then

      begin

        StrPart := LeftStr(AValue,I);

        try

          IntPart := StrToInt(RightStr(AValue,Length(AValue)-I))+1;

        except

          IntPart := 1;

          StrPart := LeftStr(AValue,I+1);

        end;

        Result := FormatFloat(Copy('000000000000',1,Length(AValue)-I),IntPart);

      end;

      Break;

    end;

  end;

end;

Delphi function for sending an email using MAPI

uses

  MAPI;

function SendMailMAPI(const Subject, Body, FileName, SenderName, SenderEMail,

                  RecepientName, RecepientEMail: String) : Integer;

var

  message: TMapiMessage;

  lpSender,

  lpRecepient: TMapiRecipDesc;

  FileAttach: TMapiFileDesc;

  SM: TFNMapiSendMail;

  MAPIModule: HModule;

begin

  FillChar(message, SizeOf(message), 0);

  with message do

  begin

    if (Subject<>'') then

    begin

      lpszSubject := PChar(Subject)

    end;

    if (Body<>'') then

    begin

      lpszNoteText := PChar(Body)

    end;

    if (SenderEMail<>'') then

    begin

      lpSender.ulRecipClass := MAPI_ORIG;

      if (SenderName='') then

      begin

        lpSender.lpszName := PChar(SenderEMail)

      end

      else

      begin

        lpSender.lpszName := PChar(SenderName)

      end;

      lpSender.lpszAddress := PChar('SMTP:'+SenderEMail);

      lpSender.ulReserved := 0;

      lpSender.ulEIDSize := 0;

      lpSender.lpEntryID := nil;

      lpOriginator := @lpSender;

    end;

    if (RecepientEMail<>'') then

    begin

      lpRecepient.ulRecipClass := MAPI_TO;

      if (RecepientName='') then

      begin

        lpRecepient.lpszName := PChar(RecepientEMail)

      end

      else

      begin

        lpRecepient.lpszName := PChar(RecepientName)

      end;

      lpRecepient.lpszAddress := PChar('SMTP:'+RecepientEMail);

      lpRecepient.ulReserved := 0;

      lpRecepient.ulEIDSize := 0;

      lpRecepient.lpEntryID := nil;

      nRecipCount := 1;

      lpRecips := @lpRecepient;

    end

    else

    begin

      lpRecips := nil

    end;

    if (FileName='') then

    begin

      nFileCount := 0;

      lpFiles := nil;

    end

    else

    begin

      FillChar(FileAttach, SizeOf(FileAttach), 0);

      FileAttach.nPosition := Cardinal($FFFFFFFF);

      FileAttach.lpszPathName := PChar(FileName);

      nFileCount := 1;

      lpFiles := @FileAttach;

    end;

  end;

  MAPIModule := LoadLibrary(PChar(MAPIDLL));

  if MAPIModule=0 then

  begin

    Result := -1

  end

  else

  begin

    try

      @SM := GetProcAddress(MAPIModule, 'MAPISendMail');

      if @SM<>nil then

      begin

        Result := SM(0, Application.Handle, message, MAPI_DIALOG or

                     MAPI_LOGON_UI, 0);

      end

      else

      begin

        Result := 1

      end;

    finally

      FreeLibrary(MAPIModule);

    end;

  end

  if Result<>0 then

  begin

    MessageDlg('Error sending mail ('+IntToStr(Result)+').', mtError, [mbOk],

               0)

  end;

end;

Delphi function to Detect if file is ReadOnly

function IsReadOnly(const FileName: string): Boolean;

var

  sr: TSearchRec;

begin

  (* Assume not read only *)

  Result := False;

  if FindFirst(FileName, faAnyFile, sr) = 0 then

  begin

    Result := (sr.Attr and faReadOnly) <> 0;

    FindClose(sr);

  end;

end;

Restrict an Delphi application to only one instance

procedure EnsureSingleInstance;

var

  Wnd: HWnd;

  WndClass, WndText: array[0..255] of char;

begin

{$ifdef Win32}

  { Try and create a semaphore. If we succeed, then check }

  { if the semaphore was already present. If it was }

  { then a previous instance is floating around. }

  { Note the OS will free the returned semaphore handle }

  { when the app shuts so we can forget about it }

  if (CreateSemaphore(nil, 0, 1,

        PChar(ExtractFileName(Application.ExeName))) <> 0) and

     (GetLastError = Error_Already_Exists) then

{$else}

  if HPrevInst <> 0 then

{$endif}

  begin

    Wnd := GetWindow(Application.Handle, gw_HWndFirst);

    while Wnd <> 0 do

    begin

      { Look for the other TApplication window out there }

      if Wnd <> Application.Handle then

      begin

        { Check it's definitely got the same class and caption }

        GetClassName(Wnd, WndClass, Pred(SizeOf(WndClass)));

        GetWindowText(Wnd, WndText, Succ(Length(Application.Title)));

        if (StrPas(WndClass) = Application.ClassName) and

           (StrPas(WndText) = Application.Title) then

        begin

          { This technique is used by the VCL: post }

          { a message then bring the window to the }

          { top, before the message gets processed }

          PostMessage(Wnd, wm_SysCommand, sc_Restore, 0);

{$ifdef Win32}

          SetForegroundWindow(Wnd);

{$else}

          BringWindowToTop(Wnd);

{$endif}

          Halt

        end

      end;

      Wnd := GetWindow(Wnd, gw_HWndNext)

    end

  end

end;