Inno-Setup检查是否有同版本应用已经安装并提供卸载选项

首先将版本号写入注册表，以便下次安装时检查

[Registry] 
;将安装路径写入注册表   
Root: HKCU; Subkey: "SOFTWARE\myprogram\config"; Flags: createvalueifdoesntexist
Root: HKCU; Subkey: "SOFTWARE\myprogram\config"; Flags: uninsdeletekeyifempty
Root: HKCU; Subkey: "SOFTWARE\myprogram\config"; ValueType: string; ValueName: "InstallPath"; ValueData: "{app}"
Root: HKCU; Subkey: "SOFTWARE\myprogram\config"; ValueType: string; ValueName: "Version"; ValueData: "{#MyAppVersion}"
Root: HKCU; Subkey: "SOFTWARE\myprogram\config"; ValueType: dword; ValueName: "VersionNum"; ValueData: "100"
Root: HKCU; Subkey: "SOFTWARE\myprogram\config"; ValueType: string; ValueName: "Release Date"; ValueData: "2018/05/29"

判断是否有相同版本应用已经被安装

[code]
//卸载时执行
procedure CurUninstallStepChanged(CurUninstallStep: TUninstallStep);
begin
    if CurUninstallStep = usDone then
    begin
       //删除 {app} 文件夹及其中所有文件
    DelTree(ExpandConstant('{app}'), True, True, True);
    end;
end;

 //初始化时执行
function InitializeSetup(): Boolean;
var
   Version: string;
   strPath: string;
   ResultCode: Integer;
begin
   Result:= TRUE;
  //read the version
  if RegQueryStringValue(HKEY_CURRENT_USER, 'SOFTWARE\myprogram\config',
     'Version', Version) then
  begin
    // Successfully read the value
    Version := Format('Exist the version %s,whether uninstall it?',[Version]);
    if MsgBox(Version,mbConfirmation,MB_YESNO) = IDYES then
    begin
     //read the path
     if RegQueryStringValue(HKEY_CURRENT_USER, 'SOFTWARE\myprogram\config',
     'InstallPath', strPath) then
        begin
         // Successfully read the value
         strPath:= strPath + '\unins000.exe';
         Exec(ExpandConstant(strPath), '', '', SW_SHOW,ewWaitUntilTerminated, ResultCode);
        end;
    end 
    else
    Result:= FALSE;
  end;
end;