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妙用Object

SilentCode 2015-10-10 18:04 原文

妙用Object

　　当你在写C#程序时，经常会用到“ToString()”这个方法，而且如果你细心你点就会发现所有的引用类型都含有“ToString()”这个方法，那么你知道为什么会这样吗？很简单，因为所有的引用类型都继承自Object这个类，而“ToString”这个方法便是Object的一个成员，所以所有的引用类型都拥有“ToString()”这个成员。接下来，我们将通过几段代码来深入理解Object的作用。

1.Object的成员：

方法 返回类型 虚拟 静态 说明
Object() N/A 无 无 System.Object类型的构造函数，由派生类的构造函数自动调用
~Object()(也称为Finalize()） N/A 无 无 System.Object类型的析构函数，由派生类的析构函数调用，不能手动调用
Equals(object) bool 有 无 把调用该方法的对象与另一对象相比，如果它们相等，就返回true。默认的实现代码会查看对象参数是否引用了同一个对象。如果想以不同的方式来比较对象，则可以重写该方法，例如，比较两个对象的状态。
Equals(object,object) bool 无 有 这个方法比较传送给它的两个对象，看看它们是否相等。检查时使用了 Equals(object) 方法。注意，如果两个对象都是空引用，这个方法就返回true。
ReferenceEquals(objcet,object) bool 无 有 这个方法比较传送给它的两个对象，看看它们是不是同一个实例的引用。
ToString() String 有 无 返回一个对应于对象实例的字符串。默认情况下，这是一个类类型限定名称，但可以重写它，给类类型提供合适的实现方式。
MemberwiseClone() object 无 无 通过创建一个新对象实例并复制成员，以复制该对象。成员不会得到这些成员的新实例。新对象的任何引用类型成员都将引用与源类型形同的对象，这个方法是受保护的，所以只能在类或派生的类中使用。
GetType() System.Type 无 无 以System.Type对对象的形式返回对象的额类型
GetHashCode() int 有 无 在需要次参数的地方，用作对象的散列函数，它返回一个以压缩形似标识的对象的值

 

2.object与自定义类型：

 

　　所有的类都继承自object类，我们自己写的类同样如此（如果你没有显示的指明基类，编译器会默认为object）。所以我们编写一些类时，可以利用object已经提供的方法。比如我们常用的“ToString”方法，通过重写，可以现实不同的字符串的版本等。object也可用于向上转型与向下转型

 

 

3.Object在事件处理时的妙用：

　　在写事件处理程序时，我们通常会这样写: public void Btn_Click(object sender,EventArgs e){}  ,第一个参数总是 object类型，为什么要这样定义？要弄懂问题，首先要知道这个“sender”所表示的含义：sender指的是调用这个事件处理程序的对象。而这样定义的好处可以通过下面的两段代码来看出：

 

建立一个winForm窗体应用程序，项目名为Calculate，下面为完整源代码（已测试）：

//项目文件 Calculate.Designer.cs
namespace Sample_Windows
{
    partial class Calculate
    {
        /// <summary>
        /// 必需的设计器变量。
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// 清理所有正在使用的资源。
        /// </summary>
        /// <param name="disposing">如果应释放托管资源，为 true；否则为 false。</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows 窗体设计器生成的代码

        /// <summary>
        /// 设计器支持所需的方法 - 不要
        /// 使用代码编辑器修改此方法的内容。
        /// </summary>
        private void InitializeComponent()
        {
            this.btn9 = new System.Windows.Forms.Button();
            this.btn8 = new System.Windows.Forms.Button();
            this.btn7 = new System.Windows.Forms.Button();
            this.btn6 = new System.Windows.Forms.Button();
            this.btn5 = new System.Windows.Forms.Button();
            this.btn4 = new System.Windows.Forms.Button();
            this.btn3 = new System.Windows.Forms.Button();
            this.btn2 = new System.Windows.Forms.Button();
            this.btn1 = new System.Windows.Forms.Button();
            this.btn0 = new System.Windows.Forms.Button();
            this.btnAdd = new System.Windows.Forms.Button();
            this.btnDiv = new System.Windows.Forms.Button();
            this.btnMul = new System.Windows.Forms.Button();
            this.btnSub = new System.Windows.Forms.Button();
            this.btnClear = new System.Windows.Forms.Button();
            this.resultBox = new System.Windows.Forms.TextBox();
            this.btnResult = new System.Windows.Forms.Button();
            this.SuspendLayout();
            // 
            // btn9
            // 
            this.btn9.Location = new System.Drawing.Point(12, 66);
            this.btn9.Name = "btn9";
            this.btn9.Size = new System.Drawing.Size(40, 31);
            this.btn9.TabIndex = 0;
            this.btn9.Text = "9";
            this.btn9.UseVisualStyleBackColor = true;
            this.btn9.Click += new System.EventHandler(this.btn9_Click);
            // 
            // btn8
            // 
            this.btn8.Location = new System.Drawing.Point(59, 66);
            this.btn8.Name = "btn8";
            this.btn8.Size = new System.Drawing.Size(40, 31);
            this.btn8.TabIndex = 1;
            this.btn8.Text = "8";
            this.btn8.UseVisualStyleBackColor = true;
            this.btn8.Click += new System.EventHandler(this.btn8_Click);
            // 
            // btn7
            // 
            this.btn7.Location = new System.Drawing.Point(105, 66);
            this.btn7.Name = "btn7";
            this.btn7.Size = new System.Drawing.Size(40, 31);
            this.btn7.TabIndex = 2;
            this.btn7.Text = "7";
            this.btn7.UseVisualStyleBackColor = true;
            this.btn7.Click += new System.EventHandler(this.btn7_Click);
            // 
            // btn6
            // 
            this.btn6.Location = new System.Drawing.Point(12, 103);
            this.btn6.Name = "btn6";
            this.btn6.Size = new System.Drawing.Size(40, 31);
            this.btn6.TabIndex = 3;
            this.btn6.Text = "6";
            this.btn6.UseVisualStyleBackColor = true;
            this.btn6.Click += new System.EventHandler(this.btn6_Click);
            // 
            // btn5
            // 
            this.btn5.Location = new System.Drawing.Point(59, 103);
            this.btn5.Name = "btn5";
            this.btn5.Size = new System.Drawing.Size(40, 31);
            this.btn5.TabIndex = 4;
            this.btn5.Text = "5";
            this.btn5.UseVisualStyleBackColor = true;
            this.btn5.Click += new System.EventHandler(this.btn5_Click);
            // 
            // btn4
            // 
            this.btn4.Location = new System.Drawing.Point(105, 103);
            this.btn4.Name = "btn4";
            this.btn4.Size = new System.Drawing.Size(40, 31);
            this.btn4.TabIndex = 5;
            this.btn4.Text = "4";
            this.btn4.UseVisualStyleBackColor = true;
            this.btn4.Click += new System.EventHandler(this.btn4_Click);
            // 
            // btn3
            // 
            this.btn3.Location = new System.Drawing.Point(12, 140);
            this.btn3.Name = "btn3";
            this.btn3.Size = new System.Drawing.Size(40, 31);
            this.btn3.TabIndex = 6;
            this.btn3.Text = "3";
            this.btn3.UseVisualStyleBackColor = true;
            this.btn3.Click += new System.EventHandler(this.btn3_Click);
            // 
            // btn2
            // 
            this.btn2.Location = new System.Drawing.Point(59, 140);
            this.btn2.Name = "btn2";
            this.btn2.Size = new System.Drawing.Size(40, 31);
            this.btn2.TabIndex = 7;
            this.btn2.Text = "2";
            this.btn2.UseVisualStyleBackColor = true;
            this.btn2.Click += new System.EventHandler(this.btn2_Click);
            // 
            // btn1
            // 
            this.btn1.Location = new System.Drawing.Point(105, 140);
            this.btn1.Name = "btn1";
            this.btn1.Size = new System.Drawing.Size(40, 31);
            this.btn1.TabIndex = 8;
            this.btn1.Text = "1";
            this.btn1.UseVisualStyleBackColor = true;
            this.btn1.Click += new System.EventHandler(this.btn1_Click);
            // 
            // btn0
            // 
            this.btn0.Location = new System.Drawing.Point(12, 177);
            this.btn0.Name = "btn0";
            this.btn0.Size = new System.Drawing.Size(40, 31);
            this.btn0.TabIndex = 9;
            this.btn0.Text = "0";
            this.btn0.UseVisualStyleBackColor = true;
            this.btn0.Click += new System.EventHandler(this.btn0_Click);
            // 
            // btnAdd
            // 
            this.btnAdd.Location = new System.Drawing.Point(151, 66);
            this.btnAdd.Name = "btnAdd";
            this.btnAdd.Size = new System.Drawing.Size(40, 31);
            this.btnAdd.TabIndex = 10;
            this.btnAdd.Text = "+";
            this.btnAdd.UseVisualStyleBackColor = true;
            this.btnAdd.Click += new System.EventHandler(this.btnAdd_Click);
            // 
            // btnDiv
            // 
            this.btnDiv.Location = new System.Drawing.Point(151, 103);
            this.btnDiv.Name = "btnDiv";
            this.btnDiv.Size = new System.Drawing.Size(40, 31);
            this.btnDiv.TabIndex = 11;
            this.btnDiv.Text = "-";
            this.btnDiv.UseVisualStyleBackColor = true;
            this.btnDiv.Click += new System.EventHandler(this.btnDiv_Click);
            // 
            // btnMul
            // 
            this.btnMul.Location = new System.Drawing.Point(151, 140);
            this.btnMul.Name = "btnMul";
            this.btnMul.Size = new System.Drawing.Size(40, 31);
            this.btnMul.TabIndex = 12;
            this.btnMul.Text = "*";
            this.btnMul.UseVisualStyleBackColor = true;
            this.btnMul.Click += new System.EventHandler(this.btnMul_Click);
            // 
            // btnSub
            // 
            this.btnSub.Location = new System.Drawing.Point(151, 177);
            this.btnSub.Name = "btnSub";
            this.btnSub.Size = new System.Drawing.Size(40, 31);
            this.btnSub.TabIndex = 13;
            this.btnSub.Text = "/";
            this.btnSub.UseVisualStyleBackColor = true;
            this.btnSub.Click += new System.EventHandler(this.btnSub_Click);
            // 
            // btnClear
            // 
            this.btnClear.Location = new System.Drawing.Point(105, 177);
            this.btnClear.Name = "btnClear";
            this.btnClear.Size = new System.Drawing.Size(40, 31);
            this.btnClear.TabIndex = 14;
            this.btnClear.Text = "C";
            this.btnClear.UseVisualStyleBackColor = true;
            this.btnClear.Click += new System.EventHandler(this.btnClear_Click);
            // 
            // resultBox
            // 
            this.resultBox.Location = new System.Drawing.Point(13, 24);
            this.resultBox.Name = "resultBox";
            this.resultBox.RightToLeft = System.Windows.Forms.RightToLeft.Yes;
            this.resultBox.Size = new System.Drawing.Size(178, 21);
            this.resultBox.TabIndex = 15;
            this.resultBox.Text = "0";
            // 
            // btnResult
            // 
            this.btnResult.Location = new System.Drawing.Point(58, 177);
            this.btnResult.Name = "btnResult";
            this.btnResult.Size = new System.Drawing.Size(40, 31);
            this.btnResult.TabIndex = 16;
            this.btnResult.Text = "=";
            this.btnResult.UseVisualStyleBackColor = true;
            this.btnResult.Click += new System.EventHandler(this.btnResult_Click);
            // 
            // Calculate
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(202, 226);
            this.Controls.Add(this.btnResult);
            this.Controls.Add(this.resultBox);
            this.Controls.Add(this.btnClear);
            this.Controls.Add(this.btnSub);
            this.Controls.Add(this.btnMul);
            this.Controls.Add(this.btnDiv);
            this.Controls.Add(this.btnAdd);
            this.Controls.Add(this.btn0);
            this.Controls.Add(this.btn1);
            this.Controls.Add(this.btn2);
            this.Controls.Add(this.btn3);
            this.Controls.Add(this.btn4);
            this.Controls.Add(this.btn5);
            this.Controls.Add(this.btn6);
            this.Controls.Add(this.btn7);
            this.Controls.Add(this.btn8);
            this.Controls.Add(this.btn9);
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedToolWindow;
            this.Name = "Calculate";
            this.Text = "Calculate";
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.Button btn9;
        private System.Windows.Forms.Button btn8;
        private System.Windows.Forms.Button btn7;
        private System.Windows.Forms.Button btn6;
        private System.Windows.Forms.Button btn5;
        private System.Windows.Forms.Button btn4;
        private System.Windows.Forms.Button btn3;
        private System.Windows.Forms.Button btn2;
        private System.Windows.Forms.Button btn1;
        private System.Windows.Forms.Button btn0;
        private System.Windows.Forms.Button btnAdd;
        private System.Windows.Forms.Button btnDiv;
        private System.Windows.Forms.Button btnMul;
        private System.Windows.Forms.Button btnSub;
        private System.Windows.Forms.Button btnClear;
        private System.Windows.Forms.TextBox resultBox;
        private System.Windows.Forms.Button btnResult;
    }
}
//项目文件 Calculate.cs
using System;
using System.Windows.Forms;

namespace Sample_Windows
{
    public partial class Calculate : Form
    {
        public Calculate()
        {
            InitializeComponent();
        }

        private string _firstNumber = String.Empty;
        private string _secondNumber = String.Empty;
        private string _operation = "+";

        private bool _flag = false;

        private void btn9_Click(object sender, EventArgs e)
        {
            if (!_flag)
            {
                _firstNumber += btn9.Text;
　　　　　　　　　　resultBox.Text=_firstNumber;
            }
            else
            {
                _secondNumber += btn9.Text;
　　　　　　　　　resultBox.Text = secondNumber;
            }
        }
......
......//此处沈略部分代码（btn8_Click,btn7_Click,btn6_Click...)
......
　　　　　private void btn0_Click(object sender, EventArgs e)
        {
            if (!_flag)
            {
                _firstNumber += btn0.Text;
　　　　　　　　　resultBox.Text=_firstNumber;
            }
            else
            {
                _secondNumber += btn0.Text;
　　　　　　　　　resultBox.Text=_secondNumber;
            }
        }

        private void btnResult_Click(object sender, EventArgs e)
        {
            if (_firstNumber != String.Empty && _secondNumber != String.Empty)
            {
                double a = Convert.ToDouble(_firstNumber);
                double b = Convert.ToDouble(_secondNumber);

                switch (_operation)
                {
                    case "+":
                        resultBox.Text = Convert.ToString(a + b);
                        break;
                    case "-":
                        resultBox.Text = Convert.ToString(a - b);
                        break;
                    case "*":
                        resultBox.Text = Convert.ToString(a*b);
                        break;
                    case "/":
                        resultBox.Text = Convert.ToString(a/b);
                        break;
                }
            }
            else
            {
                MessageBox.Show("Error!!!","Warning",MessageBoxButtons.OK,MessageBoxIcon.Warning);
            }
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            resultBox.Text = "0";
            _flag = false;
        }

        private void btnAdd_Click(object sender, EventArgs e)
        {
            _operation = "+";
            resultBox.Text = _operation;
            _flag = !_flag;
        }

        private void btnDiv_Click(object sender, EventArgs e)
        {
            _operation = "-";
            resultBox.Text = _operation;
            _flag = !_flag;
        }

        private void btnMul_Click(object sender, EventArgs e)
        {
            _operation = "*";
            resultBox.Text = _operation;
            _flag = !_flag;
        }

        private void btnSub_Click(object sender, EventArgs e)
        {
            _operation = "/";
            resultBox.Text = _operation;
            _flag = !_flag;
        }
    }
}

这是一个简单的计算器程序，在上面的代码中，共有16个事件处理程序，而其中10个数字处理程序与4个操作符处理程。看以看出代码很长，修改修改起来也很麻烦。接下来看一下下面的代码：

//项目文件 Calculate.Designer.cs
...
this.btn0.Click += new System.EventHandler(this.btn_Click);this.btn2.Click += new System.EventHandler(this.btn_Click);
this.btn3.Click += new System.EventHandler(this.btn_Click);
this.btn4.Click += new System.EventHandler(this.btn_Click);
this.btn5.Click += new System.EventHandler(this.btn_Click);
...
this.btnSub.Click += new System.EventHandler(this.btnOperation_Click);

...



//项目文件 Calculate.cs
using System;
using System.Windows.Forms;

namespace Sample_Windows
{
    public partial class Calculate : Form
    {
        public Calculate()
        {
            InitializeComponent();
        }

        private string _firstNumber = String.Empty;
        private string _secondNumber = String.Empty;
        private string _operation = "+";

        private bool _flag = false;

        private void btn_Click(object sender, EventArgs e)
        {
            Button btn = (Button) sender;   //获取触发此事件处理程序的Button对象
            if (!_flag)
            {
                _firstNumber += btn.Text;
                 resultBox.Text = _firstNumber;
           }
            else
            {
                _secondNumber += btn.Text;
                resultBox.Text = _secondNumber;
            }
        }

        private void btnResult_Click(object sender, EventArgs e)
        {
            if (_firstNumber != String.Empty && _secondNumber != String.Empty)
            {
                double a = Convert.ToDouble(_firstNumber);
                double b = Convert.ToDouble(_secondNumber);
                _firstNumber = String.Empty;
                _secondNumber = String.Empty;

                switch (_operation)
                {
                    case "+":
                        resultBox.Text = Convert.ToString(a + b);
                        break;
                    case "-":
                        resultBox.Text = Convert.ToString(a - b);
                        break;
                    case "*":
                        resultBox.Text = Convert.ToString(a*b);
                        break;
                    case "/":
                        resultBox.Text = Convert.ToString(a/b);
                        break;
                }
            }
            else
            {
                MessageBox.Show("Error!!!","Warning",MessageBoxButtons.OK,MessageBoxIcon.Warning);
            }
        }

        private void btnOperation_Click(object sender, EventArgs e)
        {
            Button btn = (Button) sender;   //获取触发此事件处理程序的Button对象
            _operation = btn.Text;
            resultBox.Text = _operation;
            _flag = !_flag;
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            _flag = false;
            resultBox.Text = "0";

        }
    }
}

 这段代码与上面要实现的功能完全一样，但只有4个时间处理程序，一个数字处理程序与一个字符处理程序，很明显，代码明显的精简的不少，而且修改起来也更加方便。从上面的例子可以看出使用object与不使用object有多么大的不同。

 

总结：

（1）在写事件处理程序时，可以将事件处理程序按事件的属性分类（如上面例子中的数字处理，操作处理，计算处理），再通过object这个类来实现用一个事件处理程序处理同一类事件。这样既避免了代码的重复，又增加了可读性和易维护性！

（2）object可以实现控件之间的交互，因为所有类都继承自object，所以通过多态性，可以将控件与object的引用绑定，以便于在不同的方法间传递，再通过向下转型解绑，就可以轻松实现控件之间的交互。

 

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