妙用Object

妙用Object

　　當你在寫C#程序時，經常會用到“ToString()”這個方法，而且如果你細心你點就會發現所有的引用類型都含有“ToString()”這個方法，那么你知道為什么會這樣嗎？很簡單，因為所有的引用類型都繼承自Object這個類，而“ToString”這個方法便是Object的一個成員，所以所有的引用類型都擁有“ToString()”這個成員。接下來，我們將通過幾段代碼來深入理解Object的作用。

1.Object的成員：

方法	返回類型	虛擬	靜態	說明
Object()	N/A	無	無	System.Object類型的構造函數，由派生類的構造函數自動調用
~Object()(也稱為Finalize()）	N/A	無	無	System.Object類型的析構函數，由派生類的析構函數調用，不能手動調用
Equals(object)	bool	有	無	把調用該方法的對象與另一對象相比，如果它們相等，就返回true。默認的實現代碼會查看對象參數是否引用了同一個對象。如果想以不同的方式來比較對象，則可以重寫該方法，例如，比較兩個對象的狀態。
Equals(object,object)	bool	無	有	這個方法比較傳送給它的兩個對象，看看它們是否相等。檢查時使用了 Equals(object) 方法。注意，如果兩個對象都是空引用，這個方法就返回true。
ReferenceEquals(objcet,object)	bool	無	有	這個方法比較傳送給它的兩個對象，看看它們是不是同一個實例的引用。
ToString()	String	有	無	返回一個對應於對象實例的字符串。默認情況下，這是一個類類型限定名稱，但可以重寫它，給類類型提供合適的實現方式。
MemberwiseClone()	object	無	無	通過創建一個新對象實例並復制成員，以復制該對象。成員不會得到這些成員的新實例。新對象的任何引用類型成員都將引用與源類型形同的對象，這個方法是受保護的，所以只能在類或派生的類中使用。
GetType()	System.Type	無	無	以System.Type對對象的形式返回對象的額類型
GetHashCode()	int	有	無	在需要次參數的地方，用作對象的散列函數，它返回一個以壓縮形似標識的對象的值

 

2.object與自定義類型：

 

　　所有的類都繼承自object類，我們自己寫的類同樣如此（如果你沒有顯示的指明基類，編譯器會默認為object）。所以我們編寫一些類時，可以利用object已經提供的方法。比如我們常用的“ToString”方法，通過重寫，可以現實不同的字符串的版本等。object也可用於向上轉型與向下轉型

 

 

3.Object在事件處理時的妙用：

　　在寫事件處理程序時，我們通常會這樣寫: public void Btn_Click(object sender,EventArgs e){}  ,第一個參數總是 object類型，為什么要這樣定義？要弄懂問題，首先要知道這個“sender”所表示的含義：sender指的是調用這個事件處理程序的對象。而這樣定義的好處可以通過下面的兩段代碼來看出：

 

建立一個winForm窗體應用程序，項目名為Calculate，下面為完整源代碼（已測試）：

//項目文件 Calculate.Designer.cs
namespace Sample_Windows
{
    partial class Calculate
    {
        /// <summary>
        /// 必需的設計器變量。
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// 清理所有正在使用的資源。
        /// </summary>
        /// <param name="disposing">如果應釋放托管資源，為 true；否則為 false。</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows 窗體設計器生成的代碼

        /// <summary>
        /// 設計器支持所需的方法 - 不要
        /// 使用代碼編輯器修改此方法的內容。
        /// </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;
    }
}

//項目文件 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;
            }
        }
......
......//此處沈略部分代碼（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;
        }
    }
}

這是一個簡單的計算器程序，在上面的代碼中，共有16個事件處理程序，而其中10個數字處理程序與4個操作符處理程。看以看出代碼很長，修改修改起來也很麻煩。接下來看一下下面的代碼：

//項目文件 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);

...



//項目文件 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;   //獲取觸發此事件處理程序的Button對象
            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;   //獲取觸發此事件處理程序的Button對象
            _operation = btn.Text;
            resultBox.Text = _operation;
            _flag = !_flag;
        }

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

        }
    }
}

 這段代碼與上面要實現的功能完全一樣，但只有4個時間處理程序，一個數字處理程序與一個字符處理程序，很明顯，代碼明顯的精簡的不少，而且修改起來也更加方便。從上面的例子可以看出使用object與不使用object有多么大的不同。

 

總結：

（1）在寫事件處理程序時，可以將事件處理程序按事件的屬性分類（如上面例子中的數字處理，操作處理，計算處理），再通過object這個類來實現用一個事件處理程序處理同一類事件。這樣既避免了代碼的重復，又增加了可讀性和易維護性！

（2）object可以實現控件之間的交互，因為所有類都繼承自object，所以通過多態性，可以將控件與object的引用綁定，以便於在不同的方法間傳遞，再通過向下轉型解綁，就可以輕松實現控件之間的交互。