innosetup 打包 安裝之前 卸載舊版本和刪除舊文件

[Code]
function InitializeSetup(): boolean;  
var  
  ResultStr: String;  
  ResultCode: Integer;  
begin  
  if RegQueryStringValue(HKLM, 'SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{9807F465-69CC-4FFE-936D-F0A5A6C09B45}_is1', 'UninstallString', ResultStr) then  
    begin  
      ResultStr := RemoveQuotes(ResultStr);  
      Exec(ResultStr, '/silent', '', SW_HIDE, ewWaitUntilTerminated, ResultCode);  
    end;  
    result := true;  
end;

procedure CurUninstallStepChanged(CurUninstallStep: TUninstallStep);
begin
  if CurUninstallStep = usDone then
    begin
    DelTree(ExpandConstant('{app}'), True, True, True);
    end;
end;