What is the meaning of this variation of the CsProj project icon in Visual Studio 2022 Solution Explorer?

I'm using VS2022 and I have a mixture of class library and executable projects in my solution. Some of the projects are SDK-Style and some are the old format. Some of the libraries target netstandard2.0, but most projects target net48. Regardless of those details, all my projects have the same green-"C#"-in-a-box icons, except the second one shown below, which has some blue symbol overlaid on it. Hovering doesn't help, they all just say "checked in". The icon in question is a project that I just modified, so I'm wondering what I might have accidentally done to summon it.

Solution

That is warning indicator that something is wrong with your csproj properties. Most of them are just resolved by just reloading it.

How to Reload:

Right click in the project click Unload Project
Right click again and then Reload project.