原文：https://stackoverflow.com/questions/13387527/add-existing-xaml-files-to-visual-studio-2012
Right-click the project and select "Unload Project"
Right-click the project node again and select "Edit [projectname].csproj"
Edit the XML, then close the file
Right-click the project node again and select "Reload Project"VS2015 将*.xaml.cs文件包裹在*.xaml文件下
原文：https://www.cnblogs.com/144823836yj/p/9204452.html