Dedicated mode not display image

```CSharp
FileCache.AppCacheMode = FileCache.CacheMode.Dedicated;
FileCache.AppCacheDirectory = DirectoryHelper.GetAppRootDirectory(".Caches/Thumbnails/");
```
`AppCacheDirectory  == "D:\\Documents\\Visual Studio 2022\\Projects\\XX\\XX\\bin\\Debug\\net6.0-windows\\.Caches\\Thumbnails\\"`

`WinINet` mode work fine.