41 C# Object Initializers

Object Initializers

With C# 3.0, initializing both objects and collections have become much easier. Consider this simple Car class, where we use the automatic properties described in a previous chapter:

class Car
{
    public string Name { get; set; }
    public Color Color { get; set; }
}

Now, in C# 2.0, we would have to write a piece of code like this to create a Car instance and set its properties:

Car car = new Car();
car.Name = "Chevrolet Corvette";
car.Color = Color.Yellow;

It's just fine really, but with C# 3.0, it can be done a bit more cleanly, thanks to the new object initializer syntax:

Car car = new Car { Name = "Chevrolet Corvette", Color = Color.Yellow };

As you can see, we use a set of curly brackets after instantiating a new Car object, and within them, we have access to all the public properties of the Car class. This saves a bit of typing, and a bit of space as well. The cool part is that it can be nested too. Consider the following example, where we add a new complex property to the Car class, like this:

class Car
{
    public string Name { get; set; }
    public Color Color { get; set; }
    public CarManufacturer Manufacturer { get; set; }
}

class CarManufacturer
{
    public string Name { get; set; }
    public string Country { get; set; }
}

To initialize a new car with C# 2.0, we would have to do something like this:

Car car = new Car();
car.Name = "Corvette";
car.Color = Color.Yellow;
car.Manufacturer = new CarManufacturer();
car.Manufacturer.Name = "Chevrolet";
car.Manufacturer.Country = "USA";

With C# 3.0, we can do it like this instead:

Car car = new Car { 
                Name = "Chevrolet Corvette", 
                Color = Color.Yellow, 
                Manufacturer = new CarManufacturer { 
                    Name = "Chevrolet", 
                    Country = "USA" 
                } 
            };

Or in case you're not too worried about readability, like this:

Car car = new Car { Name = "Chevrolet Corvette", Color = Color.Yellow, Manufacturer = new CarManufacturer { Name = "Chevrolet", Country = "USA" } };

Just like with the automatic properties, this is syntactical sugar - you can either use it, or just stick with the old, fashioned way of doing things.