C# 中委托的演变

C# 中委托的演变

 C# 1.0 中，通过使用在代码中其他位置定义的方法显式初始化委托来创建委托的实例。 

C# 2.0 引入了匿名方法的概念，作为一种编写可在委托调用中执行的未命名内联语句块的方式。

 C# 3.0 引入了 lambda 表达式，这种表达式与匿名方法的概念类似，但更具表现力并且更简练。 这两个功能统称为匿名函数。 通常，面向 .NET Framework 3.5 及更高版本的应用程序应使用 lambda 表达式。

下面的示例演示从 C# 1.0 到 C# 3.0 委托创建过程的发展：

C#复制

class Test
{
    delegate void TestDelegate(string s);
    static void M(string s)
    {
        Console.WriteLine(s);
    }

    static void Main(string[] args)
    {
        // Original delegate syntax required 
        // initialization with a named method.
        TestDelegate testDelA = new TestDelegate(M);

        // C# 2.0: A delegate can be initialized with
        // inline code, called an "anonymous method." This
        // method takes a string as an input parameter.
        TestDelegate testDelB = delegate(string s) { Console.WriteLine(s); };

        // C# 3.0. A delegate can be initialized with
        // a lambda expression. The lambda also takes a string
        // as an input parameter (x). The type of x is inferred by the compiler.
        TestDelegate testDelC = (x) => { Console.WriteLine(x); };

        // Invoke the delegates.
        testDelA("Hello. My name is M and I write lines.");
        testDelB("That's nothing. I'm anonymous and ");
        testDelC("I'm a famous author.");

        // Keep console window open in debug mode.
        Console.WriteLine("Press any key to exit.");
        Console.ReadKey();
    }
}
/* Output:
    Hello. My name is M and I write lines.
    That's nothing. I'm anonymous and
    I'm a famous author.
    Press any key to exit.
 */