C#中的Action<>和Func<>

其实他们两个都是委托【代理】的简写形式。

一、【action<>】指定那些只有输入参数，没有返回值的委托

Delegate的代码：

[csharp]
public delegate void myDelegate(string str);
public static void HellowChinese(string strChinese)
{
Console.WriteLine("Good morning," + strChinese);
Console.ReadLine();
}

myDelegate d = new myDelegate(HellowChinese);
d("Mr wang");

用了Action之后呢：

[csharp]
public static void HellowChinese(string strChinese)
{
Console.WriteLine("Good morning," + strChinese);
Console.ReadLine();
}

Action<string> action = HellowChinese;
action("Spring.");
就是相当于省去了定义委托的步骤了。

二、func<> 这个和上面的那个是一样的，区别是这个有返回值！

[csharp]
public static string HelloEnglish(string strEnglish)
{
return "Hello." + strEnglish;
}

Func<string, string> f = HelloEnglish;
Console.WriteLine(f("Srping ji"));
Console.ReadLine();


private void button5_Click(object sender, EventArgs e)

{

//类似委托功能

Func<string, int> test = TsetMothod;

Console.WriteLine(test("123"));

Func<string, int> test1 = TsetMothod;

//只需要调用这个类就可以减少重复的代码

CallMethod<string>(test1, "123");

//或者采用这种

CallMethod<string>(new Func<string, int>(TsetMothod), "123");

CallMethod(new Func<string, int>(TsetMothod), "123");

}

public static void CallMethod<T>(Func<T, int> func, T item)

{

try

{

int i = func(item);

Console.WriteLine(i);

}

catch (Exception e)

{

}

finally

{

}

}

public static int TsetMothod(string name)

{

if (string.IsNullOrEmpty(name))

{

return 1;

}

return 0;

}

----------------------------------Func例-------------------------------------------

private void button6_Click(object sender, EventArgs e)

{

// Note that each lambda expression has no parameters.

LazyValue<int> lazyOne = new LazyValue<int>(() => ExpensiveOne());

LazyValue<long> lazyTwo = new LazyValue<long>(() => ExpensiveTwo("apple"));

Console.WriteLine("LazyValue objects have been created.");

// Get the values of the LazyValue objects.

Console.WriteLine(lazyOne.Value);

Console.WriteLine(lazyTwo.Value);

}

static int ExpensiveOne()

{

Console.WriteLine("\nExpensiveOne() is executing.");

return 1;

}

static long ExpensiveTwo(string input)

{

Console.WriteLine("\nExpensiveTwo() is executing.");

return (long)input.Length;

}

}

class LazyValue<T> where T : struct

{

private Nullable<T> val;

private Func<T> getValue;

// Constructor.

public LazyValue(Func<T> func)

{

val = null;

getValue = func;

}

public T Value

{

get

{

if (val == null)

// Execute the delegate.

val = getValue();

return (T)val;

}

}

}