What does <project> is obsolete mean?

My batch build has a project, lets call it 'My.Project'. That 开发者_开发问答project got up-reved to .NET 3.5 (from .NET 1.1) in its own standalone project (meaning its not part of this batch build). Most of it is the same, there are calls that were upgraded, features added/removed. I go to start replacing all calls that all the other projects use to that, now old, project with new calls. I first remove the old reference and then add the new one. One of my projects only has one call. When I go to make the changes, one namespace in the new project throws a 'My.Project.Namespace1 is obsolete' while another call to that project throws nothing. Is there something I should be looking for? What would be causing this?

This normally means that a method being called has been marked as obsolete and therefor might get removed in future versions.

See this and this documents from MSDN about the ObsoleteAttribute and its usage.

You should see if there are other methods on the object that you can call instead and which are not obsolete.