C# 6.0 (C# vNext) 新功能之：Event initializers

事件初始化(Event initializers)

在 C# 6.0 新增功能，可以在建构实例时，直接初始化事件处理函式，如下：

例一：

new Customer { Notify += MyHandler };

例二：

var client = new WebClient
{
DownloadFileCompleted += DownloadFileCompletedHandler
};

例三：

var button = new Button { ... Click += (source, e) => ... ... };

另一个例子，在宣告事件时，直接初始化

public virtual event EventArgs RoslynReleased = delegate { };

接下来比较一下，原本的写法和新的写法：

public class Person
{
private int _age;
public int Age
{
get
{
return _age;
}
set
{
_age = value;
OnAgeChanged(EventArgs.Empty);
}
}
public string Name { get; set; }

public event EventHandler AgeChanged;
protected virtual void OnAgeChanged(EventArgs e)
{
if (AgeChanged != null)
{
AgeChanged(this, e);
}
}

public override string ToString()
{
return string.Format("Name:{0}, Age:{1}", Name, Age);
}
}

以前的写法：

var person = new Person { Age = 30, Name = "Calvin" };
person.AgeChanged += (s, e) => Console.WriteLine("Person:{0}", ((Person)s));
person.Age += 1;

新的写法：

var person2 = new Person { Age = 30, Name = "Kelly", AgeChanged += (s, e) => Console.WriteLine("Person:{0}", ((Person)s)); };
person2.Age += 1;