C# 全局变量

http://www.cnblogs.com/agian/articles/1542317.html

C#中不再有全局变量、函数或者常量。所有东西都封装在类中，包括实例成员（通过类的实例---对象可以访问）和静态成员（通过数据类型）。

这样使C#代码更加易读且有助于减少潜在的命名冲突。

1 . 可以用静态全局：public static int myPI = 3.14； 这样就可以在工程中的任何地方引用这个全局变量了 应用方法，类名.myPI

2. public class xxx

{

public static int intXXX=1;

}

用的时候

XXX X=NEW XXX();

....=X.intXXX

.......

//全局变量定义方式之一

public static string bbb; //最简单的定义全局变量的方法

//定义全局变量方式之二

public class VarTrans //用静态变量(必须使用静态变量，必须！！！)作全局变量，看看与上面的区别，上面的方法更灵活多变

{

public static string ss; //静态变量用 “类名.变量名“ 的方式访问，注意中间的点。不用采用对类进行实例引用的方式访问

}

//全局变量定义方式之三

public class MyVar //定义全局变量类。 可以赋值，但是为什么只能在赋值后读取，如何能直接读取？？？？？？？

{

private string string1;

private string string2;

private int i1;

public string String1

{

get

{

return string1;

}

set

{

string1 = value;

}

}

public string String2

{

get

{

return string2;

}

set

{

string2 = value;

}

}

public int I1

{

get

{

return i1;

}

set

{

i1 = value;

}

}

}

//以上三种定义全局变量的方法究竟都有哪些优缺点，在什么情况下使用，代码是否存在问题？？？ 需要探究！！！

//定义全局常量

public class ConsTrans

{

public const string aa = "I am Constant Var";

}

/// <summary>

/// 必需的设计器变量。

/// </summary>

private System.ComponentModel.Container components = null;

public Form1()

{

//

// Windows 窗体设计器支持所必需的

//

InitializeComponent();

//

// TODO: 在 InitializeComponent 调用后添加任何构造函数代码

//

}

/// <summary>

/// 清理所有正在使用的资源。

/// </summary>

protected override void Dispose( bool disposing )

{

if( disposing )

{

if (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.textBox1 = new System.Windows.Forms.TextBox();

this.button1 = new System.Windows.Forms.Button();

this.button2 = new System.Windows.Forms.Button();

this.button3 = new System.Windows.Forms.Button();

this.panel1 = new System.Windows.Forms.Panel();

this.label1 = new System.Windows.Forms.Label();

this.label2 = new System.Windows.Forms.Label();

this.textBox2 = new System.Windows.Forms.TextBox();

this.label3 = new System.Windows.Forms.Label();

this.panel1.SuspendLayout();

this.SuspendLayout();

//

// textBox1

//

this.textBox1.Location = new System.Drawing.Point(24, 96);

this.textBox1.Name = "textBox1";

this.textBox1.Size = new System.Drawing.Size(272, 21);

this.textBox1.TabIndex = 0;

this.textBox1.Text = "textBox1";

//

// button1

//

this.button1.Location = new System.Drawing.Point(40, 128);

this.button1.Name = "button1";

this.button1.Size = new System.Drawing.Size(240, 23);

this.button1.TabIndex = 1;

this.button1.Text = "显示全局变量存储的值";

this.button1.Click += new System.EventHandler(this.button1_Click);

//

// button2

//

this.button2.Location = new System.Drawing.Point(40, 224);

this.button2.Name = "button2";

this.button2.Size = new System.Drawing.Size(240, 23);

this.button2.TabIndex = 2;

this.button2.Text = "改变全局变量的值";

this.button2.Click += new System.EventHandler(this.button2_Click);

//

// button3

//

this.button3.Location = new System.Drawing.Point(208, 256);

this.button3.Name = "button3";

this.button3.TabIndex = 3;

this.button3.Text = "退出";

this.button3.Click += new System.EventHandler(this.button3_Click);

//

// panel1

//

this.panel1.BackColor = System.Drawing.SystemColors.ActiveCaptionText;

this.panel1.Controls.Add(this.label1);

this.panel1.Dock = System.Windows.Forms.DockStyle.Top;

this.panel1.Location = new System.Drawing.Point(0, 0);

this.panel1.Name = "panel1";

this.panel1.Size = new System.Drawing.Size(320, 56);

this.panel1.TabIndex = 4;

//

// label1

//

this.label1.Font = new System.Drawing.Font("宋体", 9F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(134)));

this.label1.Location = new System.Drawing.Point(16, 32);

this.label1.Name = "label1";

this.label1.TabIndex = 0;

this.label1.Text = "C# 全局变量实验";

//

// label2

//

this.label2.Location = new System.Drawing.Point(16, 72);

this.label2.Name = "label2";

this.label2.Size = new System.Drawing.Size(100, 16);

this.label2.TabIndex = 1;

this.label2.Text = "全局变量的值：";

//

// textBox2

//

this.textBox2.Location = new System.Drawing.Point(24, 192);

this.textBox2.Name = "textBox2";

this.textBox2.Size = new System.Drawing.Size(272, 21);

this.textBox2.TabIndex = 5;

this.textBox2.Text = "textBox2";

//

// label3

//

this.label3.Location = new System.Drawing.Point(24, 168);

this.label3.Name = "label3";

this.label3.Size = new System.Drawing.Size(100, 16);

this.label3.TabIndex = 6;

this.label3.Text = "新值：";

//

// Form1

//

this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);

this.ClientSize = new System.Drawing.Size(320, 285);

this.Controls.Add(this.label3);

this.Controls.Add(this.textBox2);

this.Controls.Add(this.panel1);

this.Controls.Add(this.button3);

this.Controls.Add(this.button2);

this.Controls.Add(this.button1);

this.Controls.Add(this.textBox1);

this.Controls.Add(this.label2);

this.Name = "Form1";

this.Text = "VarValueTrans";

this.Load += new System.EventHandler(this.Form1_Load);

this.panel1.ResumeLayout(false);

this.ResumeLayout(false);

}

#endregion

/// <summary>

/// 应用程序的主入口点。

/// </summary>

[STAThread]

static void Main()

{

Application.Run(new Form1());

}

private void button1_Click(object sender, System.EventArgs e)

{

//MyVarClass d2 = new MyVarClass();

//d2.MyString = "bbb";

//this.textBox1.Text = d2.MyString.ToString();

this.textBox1.Text = VarTrans.ss.ToString();

MessageBox.Show(this,bbb);

bbb = "changed";

}

private void Form1_Load(object sender, System.EventArgs e)

{

this.textBox1.Clear();

this.textBox2.Clear();

MyVar g_var = new MyVar();

g_var.String1 = "aaa";

g_var.String2 = "bbb";

g_var.I1 = 100;

MessageBox.Show(this,g_var.String1+" "+g_var.String2+" "+g_var.I1.ToString()+" "+ConsTrans.aa);

VarTrans.ss = "Static Var in Class 初始值";

bbb = "single static var";

}

private void button2_Click(object sender, System.EventArgs e)

{

MessageBox.Show(this,bbb);

VarTrans.ss = this.textBox2.Text.ToString();

}

private void button3_Click(object sender, System.EventArgs e)

{

this.Close();

}

}

}