Why you should be using the shiny new C# 6.0 features now!

Enterprise Software Development

@EricPhan | Chief Architect @ SSW
Why you should be
using the shiny new C#
6.0 features now!
Join the Conversation #DevSuperPowers @EricPhan

B.E. - Software Engineering, Certified Scrum Master
Eric Phan
@EricPhan
 Chief Architect @ SSW
 MCTS TFS, MCP
 Loves playing with the latest
technology

History
Summary
8 Cool C# 6.0 Features
Agenda

We’ve come a long way

History
• 2002 - C# 1.0 released with .NET 1.0 and VS2002
• First version to call Dispose on IEnumerators which
implemented IDisposable. A few other small features.
• Generics, anonymous methods, nullable types, iterator blocks
Credit to Jon Skeet - http://stackoverflow.com/a/247623

History
• Lambda expressions, extension methods, expression trees, anonymous types,
implicit typing (var), query expressions
• 2010 - C# 4.0 released with .NET 4 and VS2010
• Late binding (dynamic), delegate and interface generic variance, more COM
support, named arguments, tuple data type and optional parameters
• Async programming, caller info attributes. Breaking change: loop variable closure.

1. Auto Property Initializers

Currently
public class Developer
{
public Developer()
{
DrinksCoffee = true;
}
public bool DrinksCoffee { get; set; }
}
C# 6.0
public class Developer
{
public bool DrinksCoffee { get; set; } = true;
}
Auto Property Initializers

Auto Property Initializers
• Puts the defaults along with the declaration
• Cleans up the constructor

When I was a kid…
var devSkills =
new Dictionary<string, bool>();
devSkills["C#"] = true;
devSkills["VB.NET"] = true;
devSkills["AngularJS"] = true;
devSkills["Angular2"] = false;
Dictionary Initializers
VS2013 C# 5.0
var devSkills = new
Dictionary<string, bool>()
{
{ "C#", true },
{ "VB.NET", true },
{ "AngularJS", true },
{ "Angular2", false},
};
VS2015 C# 6.0
var devSkills =
new Dictionary<string, bool>()
{
["C#"] = true,
["VB.NET"] = true,
["AngularJS"] = true,
["Angular2"] = false
};

Dictionary Initializers
• Cleaner, less ‘{‘ and ‘}’ to try and match
• More like how you would actually use a Dictionary
• devSkills["C#"] = true;

Bad:
var firstName = "Eric";
var lastName = "Phan";
var jobTitle = "Chief Architect";
var company = "SSW";
var display = firstName + " " + lastName + ", " + jobTitle + " @ " + company;
String Interpolation
Better:
var firstName = "Eric";
var lastName = "Phan";
var jobTitle = "Chief Architect";
var company = "SSW";
var display = string.Format("{0} {1}, {3} @ {2}", firstName, lastName, company, jobTitle);

String Interpolation
• Much clearer as you can see what variables are being
used inline
• Can do formatting inline too
• {startDate:dd/MMM/yy}
• {totalAmount:c2}

public string[] GenerateCoffeeOrder(Coffee[] favCoffee)
{
var order = favCoffee.Select(x => $"{x.Name} - {x.Size}").ToArray();
return order;
}
Null Conditional Operator
What’s wrong with the above code?

{
if (favCoffee == null)
{
return null;
}
return order;
}
C# 6.0
{
var order = favCoffee?.Select(x => $"{x.Name} - {x.Size}").ToArray();
return order;
}
Fix by adding a null check

• <Variable>?.<SomePropertyOrMethod>
• “?” If the variable is null, then return null
• Otherwise execute whatever is after the “.”
• Similar to the ternary operation (conditional operator)
• var tax = hasGST
? subtotal * 1.1
: subtotal;
• Saves you many lines of null checking with just one simple character.

public event EventHandler DevSuperPowerActivated;
private void OnDevSuperPowerActivated(EventArgs specialPowers)
{
if (DevSuperPowerActivated != null) {
DevSuperPowerActivated(this, specialPowers);
}
}
C# 6.0
public event EventHandler DevSuperPowerActivated;
private void OnDevSuperPowerActivated(EventArgs specialPowers)
{
DevSuperPowerActivated?.Invoke(this, specialPowers);
}

nameOf Expression
• In the previous example, it would probably be better
to throw an exception if the parameter was null
{
if (favCoffee == null)
{
throw new ArgumentNullException("favCoffee");
}
return order;
}

nameOf Expression
• What’s the problem?
• Refactor name change
• Change favCoffee to coffeeOrders
public string[] GenerateCoffeeOrder(Coffee[] coffeeOrders)
{
if (coffeeOrders == null)
{
throw new ArgumentNullException("favCoffee");
}
var order = coffeeOrders => $"{x.Name} - {x.Size}").ToArray();
return order;
}
Not Renamed!

nameOf Expression
C# 6.0
public string[] GenerateCoffeeOrder(Coffee[] coffeeOrders)
{
if (coffeeOrders == null)
{
throw new ArgumentNullException(nameOf(coffeeOrders));
}
return order;
}

nameOf Expression
• Gives you compile time checking whenever you need
to refer to the name of a parameter

6. Expression Bodied Functions & Properties

Expression Bodied Functions & Properties
Currently
public class Coffee {
public string Name { get; set; }
public string Size { get; set; }
public string OrderDescription {
get {
return string.Format("{0} - {1}", Name, Size);
}
}
}
C# 6.0
public string OrderDescription => $"{Name} - {Size}";
}

C# 6.0
public string OrderDescription => $"{Name} - {Size}";
}
Expression Bodied Functions & Properties
name: string;
size: string;
orderDescription: () => string;
constructor() {
this.orderDescription = () => `${this.name} - ${this.size}`;
}
}
TypeScript
What language is this?

7. Exception Filters

Currently
catch (SqlException ex)
{
switch (ex.ErrorCode)
{
case -2:
return "Timeout Error";
case 1205:
return "Deadlock occurred";
default:
return "Unknown";
}
}
C# 6.0
catch (SqlException ex) when (ex.ErrorCode == -2)
{
return "Timeout Error";
}
catch (SqlException ex) when (ex.ErrorCode == 1205)
{
return "Deadlock occurred";
}
catch (SqlException)
{
return "Unknown";
}
Exception Filters

Exception Filters
• Gets rid of all the if statements
• Nice contained blocks to handle specific exception cases
Hot Tip: Special peaceful weekends exception filter*
catch (SqlException ex) when (HttpContext.Current.Identity.Name == "Boss Man"
|| DateTime.Now.DayOfWeek == DayOfWeek.Saturday
|| DateTime.Now.DayOfWeek == DayOfWeek.Sunday) {
// Do nothing
} * Disclaimer: Don’t do this

8. Static Using

C# 6.0
using static System.Math;
public double GetArea(double radius)
{
return PI * Pow(radius, 2);
}
Currently
public double GetArea(double radius)
{
return Math.PI * Math.Pow(radius, 2);
}
Static Using

Static Using
• Gets rid of the duplicate static class namespace
• Cleaner code
• Like using the With in VB.NET

There’s more too…
Await in Catch and Finally Blocks
Extension Add in Collection Initializers

Summary
• Start using these features now!
• VS 2013 + “Install-Package Microsoft.Net.Compilers”
• VS 2015 – Out of the box
• For Build server – Microsoft Build Tools 2015 or
reference the NuGet Package

With all these goodies…
• You should be 350% more productive at coding
• Get reminded about using these cool features with
ReSharper

@EricPhan #DevSuperPowers
Tweet your favourite C# 6.0 Feature
Join the Conversation #DevOps #NDCOslo @AdamCogan

Find me on Slideshare!
http://www.slideshare.net/EricPhan6

Thank you!
info@ssw.com.au
www.ssw.com.au
Sydney | Melbourne | Brisbane | Adelaide

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