C#实现中文验证码的示例代码

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }
    public string txt = "";
    private void Form1_Load(object sender, EventArgs e)
    {
        CreateImage();
    }
    private void CreateImage()
    {
        //获取GB2312编码页（表） 
        Encoding gb = Encoding.GetEncoding("gb2312");
        //调用函数产生4个随机中文汉字编码 
        object[] bytes = CreateCode(4);
        //根据汉字编码的字节数组解码出中文汉字 
        string str1 = gb.GetString((byte[])Convert.ChangeType(bytes[0], typeof(byte[])));
        string str2 = gb.GetString((byte[])Convert.ChangeType(bytes[1], typeof(byte[])));
        string str3 = gb.GetString((byte[])Convert.ChangeType(bytes[2], typeof(byte[])));
        string str4 = gb.GetString((byte[])Convert.ChangeType(bytes[3], typeof(byte[])));
        txt = str1 + str2 + str3 + str4;
        if (txt == null || txt == String.Empty)
        {
            return;
        }
        Bitmap image = new Bitmap((int)Math.Ceiling((txt.Length * 20.5)), 22);
        Graphics g = Graphics.FromImage(image);
        try
        {
            //生成随机生成器
            Random random = new Random();
            //清空图片背景色
            g.Clear(Color.White);
            //画图片的背景噪音线
            for (int i = 0; i < 2; i++)
            {
                Point tem_Point_1 = new Point(random.Next(image.Width), random.Next(image.Height));
                Point tem_Point_2 = new Point(random.Next(image.Width), random.Next(image.Height));
                g.DrawLine(new Pen(Color.Black), tem_Point_1, tem_Point_2);
            }
            Font font = new Font("宋体", 12, (FontStyle.Bold));
            LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            g.DrawString(txt, font, brush, 2, 2);
            //画图片的前景噪音点
            for (int i = 0; i < 100; i++)
            {
                Point tem_point = new Point(random.Next(image.Width),random.Next(image.Height));
                image.SetPixel(tem_point.X,tem_point.Y, Color.FromArgb(random.Next()));
            }
            //画图片的边框线
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
            pictureBox1.Image = image;
        }
        catch { }
    }

    /**/
    /* 
    此函数在汉字编码范围内随机创建含两个元素的十六进制字节数组，每个字节数组代表一个汉字，并将 
    四个字节数组存储在object数组中。 
    参数：strlength，代表需要产生的汉字个数 
    */
    public static object[] CreateCode(int strlength)
    { 
        //定义一个字符串数组储存汉字编码的组成元素 
        string[] r=new String [16]{"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"}; 
        Random rnd=new Random(); 
        //定义一个object数组用来 
        object[] bytes=new object[strlength]; 
        /**//*每循环一次产生一个含两个元素的十六进制字节数组，并将其放入bject数组中 
         每个汉字有四个区位码组成 
         区位码第1位和区位码第2位作为字节数组第一个元素 
         区位码第3位和区位码第4位作为字节数组第二个元素 
        */ 
        for(int i=0;i<strlength;i++) 
        { 
            //区位码第1位 
            int r1=rnd.Next(11,14);
            string str_r1 = r[r1].Trim(); 
            //区位码第2位 
            rnd=new Random(r1*unchecked((int)DateTime.Now.Ticks)+i);//更换随机数发生器的种子避免产生重复值 
            int r2; 
            if (r1==13) 
                r2=rnd.Next(0,7); 
            else 
                r2=rnd.Next(0,16); 
            string str_r2 = r[r2].Trim(); 
            //区位码第3位 
            rnd=new Random(r2*unchecked((int)DateTime.Now.Ticks)+i); 
            int r3=rnd.Next(10,16);
            string str_r3 = r[r3].Trim(); 
            //区位码第4位 
            rnd=new Random(r3*unchecked((int)DateTime.Now.Ticks)+i); 
            int r4; 
            if (r3==10) 
            { 
                r4=rnd.Next(1,16); 
            } 
            else if (r3==15) 
            { 
                r4=rnd.Next(0,15); 
            } 
            else 
            { 
                r4=rnd.Next(0,16); 
            }
            string str_r4 = r[r4].Trim(); 
            //定义两个字节变量存储产生的随机汉字区位码 
            byte byte1=Convert.ToByte(str_r1 + str_r2,16); 
            byte byte2=Convert.ToByte(str_r3 + str_r4,16); 
            //将两个字节变量存储在字节数组中 
            byte[] str_r=new byte[]{byte1,byte2}; 
            //将产生的一个汉字的字节数组放入object数组中 
            bytes.SetValue(str_r,i);    
        } 
        return bytes; 
   }

    private void button2_Click(object sender, EventArgs e)
    {
        CreateImage();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        if (txtCode.Text.Trim() == "")
            return;
        else
        {
            if (txtCode.Text.Trim() == txt)
            {
                MessageBox.Show("提示：验证码输入正确！","提示",MessageBoxButtons.OK,MessageBoxIcon.Information);
            }
            else
            {
                MessageBox.Show("提示：验证码输入错误，请重新输入！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }
    } 
}

partial class Form1
    {
        /// <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.pictureBox1 = new System.Windows.Forms.PictureBox();
            this.label1 = new System.Windows.Forms.Label();
            this.txtCode = new System.Windows.Forms.TextBox();
            this.button1 = new System.Windows.Forms.Button();
            this.button2 = new System.Windows.Forms.Button();
            ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).BeginInit();
            this.SuspendLayout();
            // 
            // pictureBox1
            // 
            this.pictureBox1.Location = new System.Drawing.Point(192, 18);
            this.pictureBox1.Name = "pictureBox1";
            this.pictureBox1.Size = new System.Drawing.Size(76, 21);
            this.pictureBox1.TabIndex = 0;
            this.pictureBox1.TabStop = false;
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(13, 22);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(77, 12);
            this.label1.TabIndex = 1;
            this.label1.Text = "输入验证码：";
            // 
            // txtCode
            // 
            this.txtCode.Location = new System.Drawing.Point(86, 18);
            this.txtCode.Name = "txtCode";
            this.txtCode.Size = new System.Drawing.Size(100, 21);
            this.txtCode.TabIndex = 2;
            // 
            // button1
            // 
            this.button1.Location = new System.Drawing.Point(62, 58);
            this.button1.Name = "button1";
            this.button1.Size = new System.Drawing.Size(75, 23);
            this.button1.TabIndex = 3;
            this.button1.Text = "确定";
            this.button1.UseVisualStyleBackColor = true;
            this.button1.Click += new System.EventHandler(this.button1_Click);
            // 
            // button2
            // 
            this.button2.Location = new System.Drawing.Point(143, 58);
            this.button2.Name = "button2";
            this.button2.Size = new System.Drawing.Size(75, 23);
            this.button2.TabIndex = 4;
            this.button2.Text = "刷新";
            this.button2.UseVisualStyleBackColor = true;
            this.button2.Click += new System.EventHandler(this.button2_Click);
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(283, 93);
            this.Controls.Add(this.button2);
            this.Controls.Add(this.button1);
            this.Controls.Add(this.txtCode);
            this.Controls.Add(this.label1);
            this.Controls.Add(this.pictureBox1);
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedSingle;
            this.MaximizeBox = false;
            this.Name = "Form1";
            this.Text = "中文验证码";
            this.Load += new System.EventHandler(this.Form1_Load);
            ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).EndInit();
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.PictureBox pictureBox1;
        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.TextBox txtCode;
        private System.Windows.Forms.Button button1;
        private System.Windows.Forms.Button button2;
    }