title: What C# 4.0 features can be used while still targeting the .NET 3.5 runtime?
body: <p>With C# 3.0 you could use many of its features (object initializers, var variables, lambda expressions) while still targeting .NET 2.0 or 3.0.</p>
  
  <p>What new C# 4.0 features can be used while still targeting the .NET 2.0, 3.0 or 3.5 runtimes?</p>