本文所述為C#查找素?cái)?shù)的程序代碼，包括了可視化窗體的代碼，找素?cái)?shù)的方法可以借鑒。雖然實(shí)現(xiàn)的功能簡(jiǎn)單，不過(guò)為了演示一些C#技巧，本文實(shí)例中還用到了線程技術(shù)、ListBox列表框的使用、設(shè)置程序掛起等操作，其中備有詳盡的注釋?zhuān)瑤椭蠹腋玫睦斫狻?/p>

具體實(shí)現(xiàn)代碼如下：

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Threading;
namespace SuspendAndResume
{
 public class Form1 : System.Windows.Forms.Form
 {
 private System.Windows.Forms.Label label1;
 private System.Windows.Forms.ListBox listBox1;
 private System.Windows.Forms.Button button1;
 private System.Windows.Forms.Button button2;
 private System.Windows.Forms.Button button3;
 private System.Windows.Forms.Button button4;
 private System.Windows.Forms.Label label2;
 private System.Windows.Forms.Timer timer1;
 private System.ComponentModel.IContainer components;
 //公共委托，用于輸出素?cái)?shù)
 public delegate void UD(string returnVal);
 //聲明私有線程
 private Thread pNT;
 //用于標(biāo)識(shí)是否掛起線程
 bool suspend = false;
 //用于標(biāo)識(shí)線程時(shí)候開(kāi)始運(yùn)行
 bool pNTstart = false;
 public Form1()
 {
  InitializeComponent();
  // TODO: 在 InitializeComponent 調(diào)用后添加任何構(gòu)造函數(shù)代碼
 }
 protected override void Dispose( bool disposing )
 {
  if( disposing )
  {
  if (components != null)
  {
   components.Dispose();
  }
  }
  base.Dispose( disposing );
 }
 #region Windows 窗體設(shè)計(jì)器生成的代碼
 private void InitializeComponent()
 {
  this.components = new System.ComponentModel.Container();
  this.label1 = new System.Windows.Forms.Label();
  this.listBox1 = new System.Windows.Forms.ListBox();
  this.button1 = new System.Windows.Forms.Button();
  this.button2 = new System.Windows.Forms.Button();
  this.button3 = new System.Windows.Forms.Button();
  this.button4 = new System.Windows.Forms.Button();
  this.label2 = new System.Windows.Forms.Label();
  this.timer1 = new System.Windows.Forms.Timer(this.components);
  this.SuspendLayout();
  // label1
  this.label1.Location = new System.Drawing.Point(8, 8);
  this.label1.Name = "label1";
  this.label1.TabIndex = 0;
  this.label1.Text = "已找到的素?cái)?shù)：";
  // listBox1
  this.listBox1.ItemHeight = 12;
  this.listBox1.Location = new System.Drawing.Point(8, 32);
  this.listBox1.MultiColumn = true;
  this.listBox1.Name = "listBox1";
  this.listBox1.Size = new System.Drawing.Size(272, 136);
  this.listBox1.TabIndex = 1;
  // button1
  this.button1.Location = new System.Drawing.Point(19, 184);
  this.button1.Name = "button1";
  this.button1.Size = new System.Drawing.Size(48, 23);
  this.button1.TabIndex = 2;
  this.button1.Text = "創(chuàng)建";
  this.button1.Click += new System.EventHandler(this.button1_Click);
  //
  // button2
  //
  this.button2.Location = new System.Drawing.Point(88, 184);
  this.button2.Name = "button2";
  this.button2.Size = new System.Drawing.Size(48, 23);
  this.button2.TabIndex = 3;
  this.button2.Text = "掛起";
  this.button2.Click += new System.EventHandler(this.button2_Click);
  //
  // button3
  //
  this.button3.Location = new System.Drawing.Point(157, 184);
  this.button3.Name = "button3";
  this.button3.Size = new System.Drawing.Size(48, 23);
  this.button3.TabIndex = 4;
  this.button3.Text = "恢復(fù)";
  this.button3.Click += new System.EventHandler(this.button3_Click);
  //
  // button4
  //
  this.button4.Location = new System.Drawing.Point(226, 184);
  this.button4.Name = "button4";
  this.button4.Size = new System.Drawing.Size(48, 23);
  this.button4.TabIndex = 5;
  this.button4.Text = "銷(xiāo)毀";
  this.button4.Click += new System.EventHandler(this.button4_Click);
  //
  // label2
  //
  this.label2.Location = new System.Drawing.Point(24, 224);
  this.label2.Name = "label2";
  this.label2.Size = new System.Drawing.Size(200, 23);
  this.label2.TabIndex = 6;
  this.label2.Text = "線程未啟動(dòng)";
  //
  // timer1
  //
  this.timer1.Enabled = true;
  this.timer1.Tick += new System.EventHandler(this.timer1_Tick);
  //
  // Form1
  //
  this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
  this.ClientSize = new System.Drawing.Size(292, 266);
  this.Controls.Add(this.label2);
  this.Controls.Add(this.button4);
  this.Controls.Add(this.button3);
  this.Controls.Add(this.button2);
  this.Controls.Add(this.button1);
  this.Controls.Add(this.listBox1);
  this.Controls.Add(this.label1);
  this.Name = "Form1";
  this.Text = "素?cái)?shù)";
  this.Load += new System.EventHandler(this.Form1_Load);
  this.ResumeLayout(false);
 }
 #endregion
 /// <summary>
 /// 應(yīng)用程序的主入口點(diǎn)。
 /// </summary>
 [STAThread]
 static void Main()
 {
  Application.Run(new Form1());
 }
 private void button1_Click(object sender, System.EventArgs e)
 {
  //創(chuàng)建線程實(shí)例，設(shè)置屬性
  pNT = new Thread(new ThreadStart(GPN));
  pNT.Name = "Prime Numbers Exaple";
  pNT.Priority = ThreadPriority.BelowNormal;
  //設(shè)置按鍵，停用開(kāi)始按鍵，啟用掛起按鍵和銷(xiāo)毀按鍵
  button1.Enabled = false;
  button2.Enabled = true;
  button4.Enabled = true;
  //線程開(kāi)始，并設(shè)置標(biāo)識(shí)
  pNT.Start();
  pNTstart = true;
 }
 private void button2_Click(object sender, System.EventArgs e)
 {
  //設(shè)置掛起bool變量為真
  suspend = true;
  //設(shè)置按鍵，停用掛起按鍵， 啟用恢復(fù)按鍵
  button2.Enabled = false;
  button3.Enabled = true;
 }
 private void button3_Click(object sender, System.EventArgs e)
 {
  //設(shè)置掛起bool變量為假
  suspend = false;
  //當(dāng)線程當(dāng)前狀態(tài)為掛起時(shí)，恢復(fù)該線程
  if(pNT.ThreadState == System.Threading.ThreadState.Suspended
  || pNT.ThreadState == System.Threading.ThreadState.SuspendRequested)
  {
  try
  {
   //恢復(fù)線程
   pNT.Resume();
   //設(shè)置按鍵，停用恢復(fù)按鍵，啟用掛起按鍵
   button3.Enabled = false;
   button2.Enabled = true;
  }
  catch(ThreadStateException Ex)
  {
   MessageBox.Show(Ex.ToString(), "提示");
  }
  }
 }
 private void button4_Click(object sender, System.EventArgs e)
 {
  //設(shè)置按鍵，啟用開(kāi)始按鍵，停用其他按鍵
  button1.Enabled = true;
  button2.Enabled = false;
  button3.Enabled = false;
  button4.Enabled = false;
  //銷(xiāo)毀線程
  pNT.Abort();
 }
 //GPN為GetPrimeNumber的縮寫(xiě)，用于查找并顯示素?cái)?shù)
 public void GPN()
 {
  //聲明變量
  long Counter;  //素?cái)?shù)個(gè)數(shù)
  long NumberNow;  //當(dāng)前數(shù)
  long SqrtOfNow;  //輔助數(shù)，做數(shù)組下標(biāo)
  bool IsPrime = false; //標(biāo)識(shí)是否為素?cái)?shù)
  //數(shù)組，用于存儲(chǔ)已找到素?cái)?shù)
  long[] PrimeArray = new long[256];
  //委托，用于顯示素?cái)?shù)，即將其添加到ListBox中
  string[] args = new string[] {"2"};
  UD UIDel = new UD(UpdateUI);
  //初始化，從3開(kāi)始計(jì)算，從第2個(gè)素?cái)?shù)開(kāi)始計(jì)算
  NumberNow = 3;
  Counter = 2;
  //添加2為素?cái)?shù)，放入素?cái)?shù)數(shù)組并將其顯示
  PrimeArray[1] = 2;
  this.Invoke(UIDel, args);
  //循環(huán)，用于找到并輸出256個(gè)素?cái)?shù)
  while(Counter <= 255)
  {
  IsPrime = true;
  //從1到當(dāng)前數(shù)的平方根，窮盡計(jì)算是否為素?cái)?shù)
  for(SqrtOfNow = 1; (PrimeArray[SqrtOfNow]
   * PrimeArray[SqrtOfNow] <= NumberNow);
   SqrtOfNow++)
  {
   //若能被已找到的素?cái)?shù)整除，則不是素?cái)?shù)
   if(NumberNow % PrimeArray[SqrtOfNow] == 0)
   {
   //若不是素?cái)?shù)，跳出for循環(huán)
   IsPrime = false;
   break;
   }
  }
  //若為素?cái)?shù)，將其添加到ListBox以顯示
  if(IsPrime)
  {
   //將素?cái)?shù)存入數(shù)組中儲(chǔ)存
   PrimeArray[Counter] = NumberNow;
   Counter++;
   //將素?cái)?shù)顯示到ListBox中
   args[0] = NumberNow.ToString();
   this.Invoke(UIDel,args);
   //利用bool變量，控制是否掛起線程
   if( suspend == true)
   {
   //調(diào)用Suspend方法，并捕捉異常
   try
   {
    pNT.Suspend();
   }
   catch(ThreadStateException Ex)
   {
    MessageBox.Show(Ex.ToString(), "提示");
   }
   }
   //使線程睡眠，使過(guò)程清楚顯示，且有時(shí)間掛起線程
   Thread.Sleep(500);
  }
  //除2外，素?cái)?shù)必為奇數(shù)，故跳過(guò)偶數(shù)的檢查，優(yōu)化算法
  NumberNow += 2;
  }
 }
 //更新ListBox的方法
 void UpdateUI(string result)
 {
  listBox1.Items.Add(result);
 }
 //利用Timer控件顯示線程當(dāng)前狀態(tài)
 private void timer1_Tick(object sender, System.EventArgs e)
 {
  //在線程開(kāi)時(shí)候再獲取狀態(tài)并顯示
  if( pNTstart )
  {
  label2.Text = "線程當(dāng)前狀態(tài)是：" + pNT.ThreadState.ToString();
  }
 }
 private void Form1_Load(object sender, System.EventArgs e)
 {
  //設(shè)置按鍵，啟用開(kāi)始按鍵，停用其他按鍵
  button1.Enabled = true;
  button2.Enabled = false;
  button3.Enabled = false;
  button4.Enabled = false;
 }
 }
}

感興趣的讀者可以動(dòng)手調(diào)試一下該程序代碼，相信會(huì)有一定的啟發(fā)與借鑒價(jià)值。

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