New features in C# 6.0 every Asp.Net developer should know

New features introduced in C# 5.0 or less are async and async/await, dynamic keyword, linq and so on. As such there are no major changes in C# 6.0 some syntactical improvements.

Auto property initializers

This feature enables you to assign a default value for a property as part of the property declaration. In C# 5.0 we use constructor to set a default value.

public class Person
{
 public string FirstName { get; set; } = string.Empty;
 public string LastName { get; set; } = string.Empty;
 public string FullName { get { return string.Format("{0} {1}", FirstName, LastName); } }
}

Expression bodied members

The lambda expression => here is use to set value like

public string FullName => string.Format("{0} {1}", FirstName, LastName);

Or setting given expression body functions as below

public TimeSpan GetAge() => DateTime.Now - BirthDate;

Getter-only auto-properties

While creating immutable property you can omit set accessor to create a readonly property.

public DateTime BirthDate { get; }

String interpolation

A new feature named string interpolation where string.Format call is replaced by a $ sign. Followed by array of values. Syntax is:

public string FullName => $"{FirstName} {LastName}";

Null coalescing operator - ??

This will replace if else statement with one-line conditional operator (??) checking null values and setting some default value.

var someValue = service.GetValue();

var defaultValue = 23

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

Null-conditional operators

Getting NullReferenceException while referencing a member of an object. Place a null conditional operator (?) just before member you want to reference.

var people = new List<Person>();
var name = people.FirstOrDefault()?.FullName;

Async /Await Pattern

Use the async/await pattern to allow execution of a current method while waiting for a asynchronous task to complete. Example of using async/await is while downloading a file using httpClient making a web request.

public async Task TestMethodAsync()
{
 Task<int> longRunningTask = LongRunningOperationAsync();
 
 // call await on the task 
 int result = await longRunningTask;
 
 Console.WriteLine(result);
}

public async Task<int> LongRunningMethod() // assume we return an int from this long running operation 
{
 await Task.Delay(1000); // 1 second delay
 return 1;
}

Object / array / collection initializers

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

public class Employee {
    public string FirstName {get; set;}
    public DateTime LastName {get; set;}
}

//Create an employlee by using the initializer
Employee emp = new Employee {FirstName="Shabbir", LastName="Ahmed"};

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.

Operator: as and is 

The is-operator is used to check or control if an instance is of a specific type.

if (obj is Person)
{
 //do some stuff
}

Use the as-operator while trying to cast an instance of a object to a particular class. It will return null if cast was not possible:

var emp = person as Person;
if (emp != null)
{
 //do some stuff
}

Yield-keyword

The yield-keyword lets you return an IEnumerable<T> interface from a method. The following example will return each powers of 2 up to the exponent of 8.

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

yield return adds one item to the returned IEnumerable<T> each time it is called. yield return can be very powerful as it enables you to lazily generate a sequence of objects or collection.