C# version 5.0, released with Visual Studio 2012, was a focused version of the language. Nearly all of the effort for that version went into another groundbreaking language concept: the async and await model for asynchronous programming. Here's the major features list:
The caller info attribute lets you easily retrieve information about the context in which you're running without resorting to a ton of boilerplate reflection code. It has many uses in diagnostics and logging tasks.
But async and await are the real stars of this release. When these features came out in 2012, C# changed the game again by baking asynchrony into the language as a first-class participant. If you've ever dealt with long running operations and the implementation of webs of callbacks, you probably loved this language feature.
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