Visual Studio 2012 + Serial

Current Version
Nameof
You can get the unqualified string name of a type or member for use in an error message without hard coding a string. This allows your code to remain correct when refactoring. This feature is also useful for hooking up model-view-controller MVC links and firing property changed events.
String Interpolation
You can use string interpolation expressions to construct strings. An interpolated string expression looks like a template string that contains expressions. C# creates a string by replacing the expressions with the ToString represenations of the expressions’ results. An interpolated string is easier to understand with respect to arguments than Composite Formatting.
Null-conditional Member Access and Indexing
You can test for null in a very light syntactic way before performing a member access (?.) or index (?[]) operation. These operators help you write less code to handle null checks, especially for descending into data structures. If the left operand or object reference is null, the operations returns null.
Multi-line String Literals
String literals can contain newline sequences. You no longer need the old work around of using .Value
Comments
You can put comments after implicit line continuations, inside initializer expressions, and amongst LINQ expression terms.
Smarter Fully-qualified Name Resolution
Given code such as Threading.Thread.Sleep(1000), Visual Basic used to look up the namespace "Threading", discover it was ambiguous between System.Threading and System.Windows.Threading, and then report an error. Visual Basic now considers both possible namespaces together. If you show the completion list, the Visual Studio editor lists members from both types in the completion list.
Year-first Date Literals
You can have date literals in yyyy-mm-dd format, #2015-03-17 16:10 PM#.
Readonly Interface Properties
You can implement readonly interface properties using a readwrite property. The interface guarantees minimum functionality, and it does not stop an implementing class from allowing the property to be set.
TypeOf IsNot
For more readability of your code, you can now use TypeOf with IsNot.
#Disable Warning and #Enable Warning
You can disable and enable specific warnings for regions within a source file.
XML Doc-comment Improvements
When writing doc comments, you get smart editor and build support for validating parameter names, proper handling of crefs (generics, operators, etc.), colorizing, and refactoring.
Partial Module and Interface Definitions
In addition to classes and structs, you can declare partial modules and interfaces.
#Region Directives inside Method Bodies
You can put #Region…#End Region delimiters anywhere in a file, inside functions, and even spanning across function bodies.
Overrides Definitions are Implicitly Overloads
If you add the Overrides modifier to a definition, the compiler implicitly adds Overloads so that you can type less code in common cases.
CObj Allowed in Attributes Arguments
The compiler used to give an error that CObj(…) was not a constant when used in attribute constructions.
Declaring and Consuming Ambiguous Methods from Different Interfaces
Previously the following code yielded errors that prevented you from declaring IMock or from calling GetDetails (if these had been declared in C#):
VB
Interface ICustomer
Sub GetDetails(x As Integer)
End Interface

Interface ITime
Sub GetDetails(x As String)
End Interface

Interface IMock : Inherits ICustomer, ITime
Overloads Sub GetDetails(x As Char)
End Interface

Interface IMock2 : Inherits ICustomer, ITime
End Interface