Inno Setup - How to display notifying message while installing if application is already installed on the machine?

Question

I am new to Inno Setup. I am creating an installer for my C# application using Inno Setup compiler-5.1.6.

Using my script an installer is created, and it works fine. It installs the application and can be uninstalled from control panel as well.

But my problem is that, if my application is already installed on my machine and I try to install it again it get installed without any message. It replaces the older installation.

So my requirement is that , if application is already installed , it should show me a message that "App already installed {existing version}. Do you want to replace existing installation." with 'Yes' and 'No' buttons. If user clicks 'Yes' button installer should proceed normally otherwise it should exit installation wizard without new installation.

AppVersion: it is changeable as version increases.

AppId: it will remain same for all version.

So, please can someone help me to achieve above.. Thanks in advance . .

Answer 1

Plz refer my question how to terminate installer if unstallation of legacy version of software is cancelled before executing it? , You can use same trick of checking registry for your app to check whether it is installed or not.

and to check version of app you can use following code that i got from https://blog.lextudio.com/2007/08/inno-setup-script-sample-for-version-comparison-2/:

[Code]

function GetNumber(var temp: String): Integer;
var
  part: String;
  pos1: Integer;
begin
  if Length(temp) = 0 then
  begin
    Result := -1;
    Exit;
  end;
    pos1 := Pos('.', temp);
    if (pos1 = 0) then
    begin
      Result := StrToInt(temp);
    temp := '';
    end
    else
    begin
    part := Copy(temp, 1, pos1 - 1);
      temp := Copy(temp, pos1 + 1, Length(temp));
      Result := StrToInt(part);
    end;
end;

function CompareInner(var temp1, temp2: String): Integer;
var
  num1, num2: Integer;
begin
    num1 := GetNumber(temp1);
  num2 := GetNumber(temp2);
  if (num1 = -1) or (num2 = -1) then
  begin
    Result := 0;
    Exit;
  end;
      if (num1 > num2) then
      begin
        Result := 1;
      end
      else if (num1 < num2) then
      begin
        Result := -1;
      end
      else
      begin
        Result := CompareInner(temp1, temp2);
      end;
end;

function CompareVersion(str1, str2: String): Integer;
var
  temp1, temp2: String;
begin
    temp1 := str1;
    temp2 := str2;
    Result := CompareInner(temp1, temp2);
end;

function InitializeSetup(): Boolean;
var
  oldVersion: String;
  uninstaller: String;
  ErrorCode: Integer;
begin
  if RegKeyExists(HKEY_LOCAL_MACHINE,'SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{F768F6BA-F164-4599-BC26-DCCFC2F76855}_is1') then
  begin
    RegQueryStringValue(HKEY_LOCAL_MACHINE,'SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{F768F6BA-F164-4599-BC26-DCCFC2F76855}_is1','DisplayVersion', oldVersion);
    if (CompareVersion(oldVersion, '6.0.0.1004') < 0) then
    begin
      if MsgBox('Version ' + oldVersion + ' of Code Beautifier Collection is already installed. Continue to use this old version?',mbConfirmation, MB_YESNO) = IDYES then
      begin
        Result := False;
      end
      else
      begin
          RegQueryStringValue(HKEY_LOCAL_MACHINE,'SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{F768F6BA-F164-4599-BC26-DCCFC2F76855}_is1','UninstallString', uninstaller);
          ShellExec('runas', uninstaller, '/SILENT', '', SW_HIDE, ewWaitUntilTerminated, ErrorCode);
          Result := True;
      end;
    end
    else
    begin
      MsgBox('Version ' + oldVersion + ' of Code Beautifier Collection is already installed. This installer will exit.',mbInformation, MB_OK);
      Result := False;
    end;
  end
  else
  begin
    Result := True;
  end;
end;

Answer 2

GetNumber function returns only 'major' release. To apply full Version comparison, you must concatenate Major and Minor release parts.

function GetNumber(var temp: String): Integer;
var
  part: String;
  pos1: Integer;
begin
  if Length(temp) = 0 then
  begin
    Result := -1;
    Exit;
  end;
    pos1 := Pos('.', temp);
    if (pos1 = 0) then
    begin
      Result := StrToInt(temp);
      temp := '';
    end
    else
    begin
    part := Copy(temp, 1, pos1 - 1);
      temp := Copy(temp, pos1 + 1, Length(temp));
      insert(temp, part, pos1);
      Result := StrToInt(part);
    end;
end;