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如何充分利用C#匿名方法的平台优势

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我希望本文已经说明如何使用匿名方法。虽然它们还不是革命性的，但是它们是C#演化成为一门程序员友好的语言过程中的一个重要步骤。

作者：Builder.com.cn 2007年7月31日

关键字： Office

例3——参数的传递

你可以将参数传递给匿名方法，方式就和你处理引用命名方法参数的委托一样。下面的示例3说明这种类型的功能：

示例列表3

   #region Parameter example - Example3
   privatedelegatevoidExample3(string firstName, string lastName);

   privatevoid btnExample3_Click(object sender, EventArgs e)
   {
       //Setup our parameters.
       string parameter1 = "Zach";
       string parameter2 = "Smith";

       //Create an instance of the Example3 delegate with an
       // anonymous method.
       Example3 example =
           newExample3(
               delegate(string firstName, string lastName)
               {
                   MessageBox.Show("Example3: " + firstName + " " + lastName);
               });

       //Execute the delegate.
       example(parameter1, parameter2);
   }
   #endregion

例4——多个方法的关联

就和命名方法一样，将多个匿名方法与同一个委托进行关联是可能的。这在很多情况下会非常有用——首先想到的是把一个简单的处理程序添加给按钮的点击事件。下面的代码（示例4）显示了一个委托，它同时带有与之相关联一个匿名方法和一个命名方法：

示例列表4

   #region Multiple method association (stacking) - Example4
   privatedelegatevoidExample4(string firstName, string lastName);

   privatevoid btnExample4_Click(object sender, EventArgs e)
   {
       //Setup our parameters.
       string parameter1 = "Zach";
       string parameter2 = "Smith";

       //Create an instance of the Example4 delegate with an
       // anonymous method.
       Example4 example =
           newExample4(
               delegate(string firstName, string lastName)
               {
                   MessageBox.Show("Example4: " + firstName + " " + lastName);
               });

       //Add another method to the delegate - this time
       // a named method.
       example += newExample4(Example4NamedMethod);

       //Execute the delegate.
       example(parameter1, parameter2);
   }

   privatevoid Example4NamedMethod(string firstName, string lastName)
   {
       MessageBox.Show("Example4Method: " + firstName + " " + lastName);
   }
   #endregion

例5——将匿名方法作为参数传递

就和命名方法一样，将匿名方法作为参数传递给函数是可能的。这并不是一个我认为会通常使用的特性，但是我敢肯定未来会有这种需要。下面的代码（例5）说明了这种类型的功能，它将一个命名方法作为参数传递给了函数：

示例列表5

   #region Passing anonymous methods - Example5
privatedelegatevoidExample5(string firstName, string lastName);

   privatevoid btnExample5_Click(object sender, EventArgs e)
   {
       //Execute Passit and pass the anonymous method.
       Passit((Example5)delegate(string firstName, string lastName)
               {
                   MessageBox.Show("Example5: " + firstName + " " + lastName);
               });

       //Execute Passit with the named method.
       Passit(Example5NamedMethod);
   }

   privatevoid Example5NamedMethod(string firstName, string lastName)
   {
       MessageBox.Show("Example5Method: " + firstName + " " + lastName);
   }

   privatevoid Passit(Example5 example)
   {
       example("Zach", "Smith");
   }
   #endregion

例6—－访问类成员

这是对上面例2的变量范围的扩展。但是，这个例子（例6）说明了匿名参数还能够在它们的代码块之外执行命名方法：

示例列表6

    #region Accessing class members - Example6
    privatedelegatevoidExample6();

    privateint _customerId;
    privatestring _customerCode;

    publicint CustomerID
    {
        get { return _customerId; }
        set { _customerId = value; }
    }

    publicstring CustomerCode
    {
        get { return _customerCode; }
        set { _customerCode = value; }
    }

    privatevoid btnExample6_Click(object sender, EventArgs e)
    {
        //Populate out properties.
        this.CustomerID = 90;
        this.CustomerCode = "1337HK";

        //Setup the delegate/anonymous method.
        Example6 example =
            newExample6(
                delegate
                {
                    this.ShowCustomer(this.CustomerID, this.CustomerCode);
                });

        //Execute the delegate.
        example();

        //Change the properties.
        this.CustomerID = 54;
        this.CustomerCode = "L4M3";

        //Execute the delegate again.
        // Notice that the new values are reflected.
        example();
    }

    privatevoid ShowCustomer(int customerId, string customerCode)
    {
        MessageBox.Show(
            String.Format("CustomerID: {0} Customer Code: {1}",
                            customerId, customerCode));
    }
    #endregion