An explanation of Object Initialisers in C#?

C开发者_StackOverflowould someone please provide a explanation of Object Initialisers in C# and examples if possible.

So far I understand that they allow you to condense instances of a class, is this correct?

---

Object initializers was added to C# in version 3, and provide condensed object initialization syntax. They are nothing but syntactic sugar, meaning they allow you to express the same code shorter than before.

Here is an example:

Foo foo = new Foo { Name = "John", Age = 42 };

Which is the equivalent of:

Foo foo = new Foo();
foo.Name = "John";
foo.Age = 42;

Have a look on the official documentation here.

A related feature is collection initializers, which lets you initialize collections easily:

var names = new List<string> { "John", "Michael", "Joe" }

The above code is short hand for constructing a new List, and then adding each element to it. For collection initializers to work for a type, nothing more is required than a public Add method taking the correct type as the parameter.

---

Object initializers let you assign values to any accessible fields or properties of an object at creation time without having to explicitly invoke a constructor.

Cat cat = new Cat { Age = 10, Name = "Fluffy" };

---

Refer to Object and Collection Initializers (C# Programming Guide).

---

Object Initialisers allow you to set the properties of an instance when you declare it. For example:

class House
{
    public int Rooms { get; set; }
    public int PeopleLiving { get; set; }
}

Then using this:

House h = new House { Rooms = 4, PeopleLiving = 5 }

Simply sets these values when you create the object, a bit like a constructor where you can choose which properties to set. You can also use a constructor as well:

House h = new House("10 Some Road", "Some City") { Rooms = 4, PeopleLiving = 5 }

---

This is actually just syntactic sugar, the compiler converts it to this equivalent C# code:

House h = new House();
h.Rooms = 4;
h.PeopleLiving = 5;

---

From the MSDN

Object initializers let you assign values to any accessible fields or properties of an object at creation time without having to explicitly invoke a constructor.

All this means is that it's a convenient shortcut you can use to (hopefully) make your code more readable. The example they give:

Cat cat = new Cat { Age = 10, Name = "Fluffy" };

would be more traditionally written as:

Cat cat = new Cat();
cat.Age = 10;
cat.Name = "Fluffy";

or

Cat = new Cat(10, "Fluffy");

The former can be more long winded, and there is a difference between the compiled code (thanks to @Kirk Woll for the link), explained in this post. The initialiser creates a temporary variable, assigns the properties and then copies that to the real variable. Something like this:

Cat temporaryCat = new Cat();
temporaryCat.Age = 10;
temporaryCat.Name = "Fluffy";
Cat cat = temporaryCat;

The latter would (before C# 4.0 with optional arguments) require you to have a many overloaded versions of your constructor for each possible parameter combination.