New C# 7.0 features in Visual Studio “15” Preview 4

Visual Studio Blog

Over the past couple of previews, new C# language features have been trickling in, but Preview 4 marks a point where the majority of C# 7.0 are now available.

Here’s a code sample that uses a good number of these features, and that works in Preview 4 today:

class Program


    static void Main(string[] args)


        object[] numbers =

            { 0b1, 0b10, new object[] { 0b100, 0b1000 },   // binary literals

             0b1_0000, 0b10_0000 };                        // digit separators

        var (sum, count) = Tally(numbers);                 // deconstruction

        WriteLine($"Sum: {sum}, Count: {count}");


    static (int sum, int count) Tally(object[] values)     // tuple types


        var r = (s: 0, c: 0);                              // tuple literals

        void Add(int s, int c) { r = (r.s + s, r.c + c); } // local functions

        foreach (var v in values)


            switch (v)                                     // switch on any value


                case int i:                                // type patterns

                    Add(i, 1);


                case object[] a when a.Length > 0:         // case conditions

                    var t = Tally(a);

                    Add(t.sum, t.count);




        return r;



For a full write-up about tuples, deconstruction, pattern matching, local functions, and the rest of C# 7.0, head over to the .NET Blog.

Earlier versions of some of these features were shown at Build 2016.

Happy hacking!

Mads Torgersen, C# Language Program Manager @MadsTorgersen

Mads leads the design of the C# language. During his 11 years at Microsoft he also contributed to Typescript, Roslyn, Visual Basic, and LINQ. Before that he was a professor at Aarhus University, doing research on programming languages and type systems.


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