嗨朋友，

感谢您在MSDN论坛上发帖。

Thank you for posting in MSDN forum.

直接 迁移项目完全没问题从.Net Framework 4.5到4.6。

It's totally ok to directly migrate project from .Net Framework 4.5 to 4.6.

.NET Framework 4.5及更高版本向后兼容使用早期版本的.NET Framework构建的应用程序。换句话说，使用以前版本构建的应用程序和组件无需在.NET Framework
4.5及更高版本上进行修改即可使用。

The .NET Framework 4.5 and later versions are backward-compatible with apps that were built with earlier versions of the .NET Framework. In other words, apps and components built with previous versions will work without modification on the .NET Framework 4.5 and later versions.

参考：
.NET Framework中的版本兼容性

最诚挚的问候，