.NET Framework 4.0 shipped concurrently with new versions of Microsoft’s primary development languages:

One of the most marketed features of v4.0 was the focus on multi-core processing.

Microsoft officially ended extended support for .NET Framework 4.0 on .

Unlike versions 3.0 and 3.5 (which built upon the CLR from version 2.0), .NET Framework 4.0 introduced a new version of the CLR (CLR 4). This allowed for side-by-side hosting, meaning applications built on 4.0 could run alongside older versions without conflict.