Overview
C# 3.0 adds several new language features. In this article I will review Auto Implemented Properties, Object Initializers, Collection Initializers, Local Variable Type Inference, Language Integrated Query (LINQ) and Anonymous Types.
I picked up this material from an excellent video by Luke Hoban.
Auto Implemented Properties
public string CustomerID { get; set; }
The private variable is no longer necessary.
Object Initializers
Customer cust1 = new Customer()
{ CustomerID = "ALKI", ContactName = "Marcel" };
Even if a method doesn't have an overload which lets you fill in some properties right away, you can use the Object Initializer to accomplish the same thing.
Collection Initializer
new List<Customer>() { cust1 };
As above but for collections.
Local Variable Type Inference
var customers = new List<Customer>();
How sweet is this?! But, only for local types. You won't be doing this with class level variables.
Language Integrated Query (LINQ)
Enumerable.Where(customers, c=>c.city == "London");
customers.Where(c=>c.city == "London");
var query = from c in customers
where c.City == "London"
Select c;
Where is an extension method
LINQ uses Lambda expressions. Here c=> c.city == "London" is the Lambda expression. The => is read "goes to."
LINQ can be used to query against XML, objects or SQL.
Anonymous Type
The neat thing about anonymous types is that you can create a type on the fly with no name/type, hence anonymous. This new type can have a different number of properties than the query source. For example, say you're doing a query on the customer object, the query result can be set up to only contain the customer ID and name.
Var query ...
select new
{ CustomerID = c.CustomerID,
ContactName = c.ContactName };
// the property names above are optional, if not specified the property name of source object is used.
