Edit & Continue: Allow the modification of lambda's and anonymous methods
Edit and Continue has always been a staple of Visual Studio development; it's one of the most important features that make it better than other IDEs. In 2002, Visual Studio .Net came out, and didn't have Edit and Continue, which made it very hard to use. In 2003, the new version had Edit and Continue and I was jubilant.
Enable edit and continue for lambda changes; that might mean that you even have to allow edit and continue to add new methods, but that should be possible using light-weight code generation.
(Filed on behalf of "The Configurator": https://visualstudio.uservoice.com/admin/users/14358195-the-configurator)