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

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，可以在建構實例時，直接初始化事件處理函式，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) => ... ... };

另一個例子，在宣告事件時，直接初始化

public virtual event EventArgs RoslynReleased = delegate { };

接下來比較一下，原本的寫法和新的寫法：

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);
    }
}

以前的寫法：

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

新的寫法：

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