如何检测用户是否已经安装了软件,如果是这样,如何提供删除旧版本的可能性？

我已经写了一些行来检查.现在是否正确？如果这是正确的,那么如何让用户选择是否要继续安装或卸载旧版本？

#define UNINSTKEY "Software\Microsoft\Windows\CurrentVersion\Uninstall\setupname_is1"
var:
    uninstallPath: string;

Function InitializeSetup: Boolean;
begin
    if(RegQueryStringValue(HKLM,'{#UNINSTKEY}','UninstallString',uninstallPath)) and (uninstallPath <> '') and (fileexists(uninstallPath)) then
    begin
      Result := (MsgBox(CustomMessage('NotVerifiedVersionFound'),mbConfirmation,MB_YESNO or MB_DEFBUTTON2) = IDYES);
    end
// ...
end

您可以使用Craig McQueen最初发布的解决方案： InnoSetup: How to automatically uninstall previous installed version?

function GetUninstallString: string;
var
  sUnInstPath: string;
  sUnInstallString: String;
begin
  Result := '';
  sUnInstPath := ExpandConstant('Software\Microsoft\Windows\CurrentVersion\Uninstall\{{A227028A-40D7-4695-8BA9-41DF6A3895C7}_is1'); //Your App GUID/ID
  sUnInstallString := '';
  if not RegQueryStringValue(HKLM,sUnInstPath,sUnInstallString) then
    RegQueryStringValue(HKCU,sUnInstallString);
  Result := sUnInstallString;
end;

function IsUpgrade: Boolean;
begin
  Result := (GetUninstallString() <> '');
end;

function InitializeSetup: Boolean;
var
  V: Integer;
  iResultCode: Integer;
  sUnInstallString: string;
begin
  Result := True; // in case when no prevIoUs version is found
  if RegValueExists(HKEY_LOCAL_MACHINE,'Software\Microsoft\Windows\CurrentVersion\Uninstall\{A227028A-40D7-4695-8BA9-41DF6A3895C7}_is1','UninstallString') then  //Your App GUID/ID
  begin
    V := MsgBox(ExpandConstant('hey! An old version of app was detected. Do you want to uninstall it?'),mbinformation,MB_YESNO); //Custom Message if App installed
    if V = IDYES then
    begin
      sUnInstallString := GetUninstallString();
      sUnInstallString :=  RemoveQuotes(sUnInstallString);
      Exec(ExpandConstant(sUnInstallString),'',SW_SHOW,ewWaitUntilTerminated,iResultCode);
      Result := True; //if you want to proceed after uninstall
      //Exit; //if you want to quit after uninstall
    end
    else
      Result := False; //when older version present and not uninstalled
  end;
end;