If you start exploring C# or decide to expand your knowledge, you should learn these useful language features, which will help you to simplify the code, avoid errors and save a lot of time.

1) async / await

Use the async / await-pattern to allow unblocking of the UI / current thread when execution blocking operations. The async / await-pattern works by letting the code continue executing even if something is blocking the execution (like a web request).

Read more about the async / await-pattern here: https://msdn.microsoft.com/en-us/library/hh191443.aspx

2) Object / array / collection initializers

Create instances of classes, arrays and collections easily by using the object, array and collection initializers:

//Just some demo class
public class Employee {
    public string Name {get; set;}
    public DateTime StartDate {get; set;}
}

//Create an employlee by using the initializer
Employee emp = new Employee {Name="John Smith", StartDate=DateTime.Now()};

The above example can be really useful in unit testing but should be avoided in other contexts as instances of classes should be created using a constructor.

Read more about initializers here: https://msdn.microsoft.com/en-us/library/bb384062.aspx

3) Lambdas, predicates, delegates and closures

These features are practically a necessity in many cases (e.g. when using Linq), make sure to actually learn when and how to use them.

Read more about Lambdas, predicates, delegates and closure here: http://www.codeaddiction.net/articles/13/lambda-expressions-delegates-predicates-and-closures-in-c

4) ?? (Null coalescing operator)

The ??-operator returns the left side as long as it’s not null, in that case the right side will be returned:

//May be null
var someValue = service.GetValue();
var defaultValue = 23

//result will be 23 if someValue is null
var result = someValue ?? defaultValue;

The ??-operator can be chained:

string anybody = parm1 ?? localDefault ?? globalDefault;

And it can be used to convert nullable types to non nullable:

var totalPurchased = PurchaseQuantities.Sum(kvp => kvp.Value ?? 0);

Read more about the ??-operator here: https://msdn.microsoft.com/en-us/library/ms173224.aspx

5) $”{x}” (String Interpolation) – C# 6

A new feature of C# 6 that lets you assemble strings in an efficient and elegant way:

//Old way
var someString = String.Format("Some data: {0}, some more data: {1}", someVariable, someOtherVariable);

//NewWay
var someString = $"Some data: {someVariable}, some more data: {someOtherVariable}";

You can put C# expressions in between the braces, which makes this very powerful.

6) ?. (Null-conditional operator) – C# 6

The null-conditional operator works like this:

//Null if customer or customer.profile or customer.profile.age is null
var currentAge = customer?.profile?.age;

No more NullReferenceExceptions!

Read more about the ?.-operator here: https://msdn.microsoft.com/en-us/library/dn986595.aspx

7) nameof Expression – C# 6

So the new nameof-expression might not seem important, but it really has it value. When using automatic re-factoring tools (like ReSharper) you sometime need to refer to a method argument by it’s name:

public void PrintUserName(User currentUser)
{
    //The refactoring tool might miss the textual reference to current user 
    below if we're renaming it
    if(currentUser == null)
        _logger.Error("Argument currentUser is not provided");

    //...
}

This is how you should use it…

public void PrintUserName(User currentUser)
{
    //The refactoring tool will not miss this...
    if(currentUser == null)
        _logger.Error($"Argument {nameof(currentUser)} is not provided");

    //...
}

Read more about the nameof-expression here: https://msdn.microsoft.com/en-us/library/dn986596.aspx

8) Property Initializers – C# 6

Property initializers lets you declare an initial value for a property:

public class User
{ 
    public Guid Id { get; } = Guid.NewGuid();
    // ...
}

A benefit of using property initializers is that you can not declare a set:er, thus making the property immutable. Property initializers works great together with C# 6 primary constructor syntax.

9) as and is-operators

The is-operator is used to control if an instance is of a specific type, e.g. if you want to see if a cast is possible:

if (Person is Adult)
{
    //do stuff
}

Use the as-operator to try to cast an instance to a class. It will return null if cast was not possible:

SomeType y = x as SomeType;
if (y != null)
{
    //do stuff
}

10) yield-keyword

The yield-keyword lets you feed an an IEnumerable-interface with items. The following example will return each powers of 2 up to the exponent of 8 (e.g. 2, 4, 8, 16, 32, 64, 128 ,256):

public static IEnumerable Power(int number, int exponent)
{
    int result = 1;
    for (int i = 0; i < exponent; i++)
    {
      result = result * number;
      yield return result;
    }
}

yield return can be very powerful if it’s used in the correct way. It enables you to lazily generate a sequence of objects, ie. the system does not have to enumerate the whole collection – it can be done on demand.

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