C# Today and Tomorrow

Editor's Notes

1. Evolve: it’s now easier to evolve the languages Enable: it enables a whole ecosystem of code analysis, refactoring tools, and tools that act on code Dogfood: we can roll out new language features and tooling to early adopters for feedback without having to ship VS or compilers
2. Pace of innovation is not necessarily whenever you get an idea. There’s such a thing as an innovation that comes too soon. The evolution comparison is also interesting because it’s the environment that drives innovation, not random mutations. Horseshoe crab picture by Didier Descouens (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons Saddleback caterpillar picture by Mary Keim https://www.flickr.com/photos/38514062@N03/9410316517/in/photolist-fkykfv-fkyk58-fpYfpv https://creativecommons.org/licenses/by-nc-sa/2.0/
3. Launch VS, open REPL (view/other windows/c# interactive) 2+2, Console.WriteLine(“Hello SpaceX”) – Remember, Alt+up arrow to copy a previous statement. CTRL+Enter to execute no matter where the cursor is. using static System.Console; Console.WriteLine(“Hello SpaceX”) <- Roslyn tells you what became unnecessary. Hover to see recommendation. Remove “Console” Interpolating strings should be easy: Add the $ in front of the string, and start introducing expressions: {2016} at the end of the string. Replace expression with {2015+1} Make it reusable next year by writing{DateTime.Now.Year} You can also declare variables in the REPL:var awesomeCompany = “SpaceX”; and then replace the static string. Let’s define a method now: take the previsous code and change it to:string Greeting() {return $”Hello {awesomeCompany} {DateTime.Now.Year}”;}then call Greeting() Change it to a expression-bodied function:string Greeting() => $"Hello { awesomeCompany} { DateTime.Now.Year}"; Let’s look at other C#6 features. First, auto-property initializers:public class Person{ public string FirstName { get; } = "Brett";}new Person().FirstNameYou can also set such properties from a constructor, which is nice as it removes the need for a private setter that you never don’t need. You can replace the property definition withpublic string FirstName => "Brett"; Add the following members to the class to introduce the null-coalesce operator:public string LastName { get; set; }public string Initials => FirstName?[0].ToString() + LastName?[0].ToString();then do new Person().Initialsthen new Person { LastName = "Morrison" }.Initials We have a new operator that can make a lot of refactoring scenarios more robust: nameofnameof(Person)string Greeting(string awesomeCompany) => $"Hello {nameof(awesomeCompany)} { awesomeCompany } { DateTime.Now.Year }";Refactoring is going to work inside string interpolation. Index initializers:var numbers = new Dictionary<int, string>{ [1] = "One", [42] = "Forty-two“};numbers[42] Other C#6 features include await in catch blocks, and “when” conditions on catch.
4. Closest current equivalent code is var p = o as Point; if (p != null) {… but that gives p too large a scope.
5. Alternative today is to declare a small class, or have out parameters. The syntax is designed to mirror that of function arguments.
6. String! Could have been another solution, but would have implied that non-nullable is the exception. Having string? makes nullable strings the exception, as it should have been from the start, but enforcing string without qualifiers to be non-nullable would have been far too breaking. In the end, emitting warnings for failures to check for null is a good compromise as it encourages the right behavior without breaking existing code.