ItemControl实现列表和多层嵌套(Prism Mvvm)

# Prism.Unity Thank you for installing Prism 8.1! ## Help Support Prism While Prism is, and will continue to be totally free to download, Open Source is not free. If you or your company have the resources, please consider becoming a GitHub Sponsor. GitHub Sponsorships help to make Open Source Development more sustainable. Depending on your Sponsorship Tier, you may also get access to some great benefits on Sponsor Connect (https://sponsorconnect.dev) including: - The Sponsor Only Discord server - CI Packages for Prism (get bug fixes as they are merged!) - Training available ONLY to sponsors on Sponsor Connect https://xam.dev/sponsorbrian https://xam.dev/sponsordan ## Support & FAQ 1) Support: Prism is distributed under the MIT License this means "AS IS", WITHOUT WARRANTY OF ANY KIND. If you require code level support, architectural guidance, or custom builds of Prism, please reach out at https://avantipoint.com/contact to inquire about Enterprise support options. 2) Community Support: GitHub issues are not the place to ask questions, these are reserved for feature requests and legitimate bug reports. You are free to ask questions on Stack Overflow however the Prism team does not monitor questions posted there. We do encourage you to post questions using GitHub Discussions on the main Prism repo. If you see a question that you know the answer to please pay it forward and help other developers that may just be starting out. https://github.com/PrismLibrary/Prism/discussions 3) Reporting Bugs: If you believe you have encountered a bug, please be sure to search the open and closed issues as you may find the issue has already been fixed as and is awaiting release. If you find that you have a new issue, please create a new project that focuses on ONLY the necessary steps to reproduce the issue you are facing. Issues that are opened which do not have a sample app reproducing the issue will be closed. In addition to this being required by the Prism team, this is just good etiquette for any Open Source project. Additionally we ask that you do not try to be an Archaeologist, trying to comment on PR's, commits and issues from long ago, if there is a legitimate issue, open a new issue referencing what you need to reference. Archaeologists will be ignored. 4) Samples: Currently the Prism team maintains a wide variety of samples for WPF and Xamarin.Forms. If you would like to help give back, and help build out a samples repo for Uno Platform, WinUI, or .NET Maui please contact the Prism team via Twitter or Discord.