iOS Question Problem with WebView Component

I wrote an app which will load html file from File.DirAssets with Webview controller, code user is:

webview1.LoadUrl("file://" & File.Combine(File.DirAssets, FileName))

When I use debug mode, program runs correctly. But when I build release version and run it, the webview cannot show the html page, what's wrong?
Probably I think the problem is the folder "DirAssets", but it works in B4A and B4i debug mode, so there is a solution to this problem?

Thanks