c#实现验证码功能
一、验证码简介
验证码功能一般是用于防止批量注册的,不少网站为了防止用户利用机器人自动注册、登录、灌水,都采用了验证码技术。所谓验证码,就是将一串随机产生的数字或字母或符号或文字,生成一幅图片, 图片里加上一些干扰象素(防止OCR),由用户肉眼识别其中的验证码信息,输入表单提交网站验证,验证成功后才能使用某项功能。
常见的验证码有如下几种:
1、纯数字验证码,一般为四位随机数字;
2、数字+字母验证码,一般从数字(0~9)和字母(A~Z和a~z)中随机抽出几个字符组成;
3、汉字验证码,相对而言,这种验证码比较少见一点,实现起来也相对复杂一些,但在不少网站中还是可以看到的;
二、验证码的实现
1、纯数字验证码的实现
纯数字验证码的实现相对比较简单,可通过以下两种方法来实现
(1)使用随机数方式,代码如下:
- private String GetRandomint(int codeCount)
- {
- Random random = new Random();
- string min = "";
- string max = "";
- for (int i = 0; i < codeCount; i++)
- {
- min +="1";
- max+="9";
- }
- return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());
- }
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(2)使用随机组合方式,代码如下:
- private string CreateRandomCode(int codeCount)
- {
- string allChar = "0,1,2,3,4,5,6,7,8,9";
- string[] allCharArray = allChar.Split(',');
- string randomCode = "";
- int temp = -1;
- Random rand = new Random();
- for (int i = 0; i < codeCount; i++)
- {
- if (temp != -1)
- {
- rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
- }
- int t = rand.Next(9);
- if (temp == t)
- {
- return CreateRandomCode(codeCount);
- }
- temp = t;
- randomCode += allCharArray[t];
- }
- return randomCode;
- }
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2、数字+字母验证码的实现,代码如下:
- private string CreateRandomCode(int codeCount)
- {
- string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";
- string[] allCharArray = allChar.Split(',');
- string randomCode = "";
- int temp = -1;
- Random rand = new Random();
- for (int i = 0; i < codeCount; i++)
- {
- if (temp != -1)
- {
- rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
- }
- int t = rand.Next(61);
- if (temp == t)
- {
- return CreateRandomCode(codeCount);
- }
- temp = t;
- randomCode += allCharArray[t];
- }
- return randomCode;
- }
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3、汉字验证码的实现,代码如下:
- /**/
- /*
- 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[] CreateRegionCode(int strlength)
- {
- //定义一个字符串数组储存汉字编码的组成元素
- string[] rBase = 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 = rBase[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 = rBase[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 = rBase[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 = rBase[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;
- }
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三、具体实例
前台代码display.aspx
- <body>
- <form id="form1" runat="server">
- <div>
- <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
- <asp:Image ID="Image1" runat="server" ImageUrl="png.aspx" /><br />
- <br />
- <asp:Button ID="Button2" runat="server" OnClick="Button2_Click" Text="Button" />
- <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
- <asp:ListItem Value="3">默认</asp:ListItem>
- <asp:ListItem Value="1">文字</asp:ListItem>
- <asp:ListItem Value="2">数字</asp:ListItem>
- <asp:ListItem Value="3">混合</asp:ListItem>
- </asp:DropDownList></div>
- </form>
- </body>
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后台代码display.cs
- protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
- {
- switch (DropDownList1.SelectedValue)
- {
- case "1":
- Image1.ImageUrl = "png.aspx?aa=1";
- break;
- case "2":
- Image1.ImageUrl = "png.aspx?aa=2";
- break;
- case "3":
- Image1.ImageUrl = "png.aspx?aa=3";
- break;
- }
- }
- protected void Button2_Click(object sender, EventArgs e)
- {
- if (TextBox1.Text == Session["gif"].ToString())
- Response.Write("OK,正确");
- else
- Response.Write("验证码不符合");
- }
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后台代码png.cs
- public partial class png : System.Web.UI.Page
- {
- protected void Page_Load(object sender, EventArgs e)
- {
- switch (Request.QueryString["aa"])
- {
- case "1":
- gif = stxt(10);
- Session["gif"] = stxt(10);
- break;
- case "2":
- gif = GetRandomint(4);
- Session["gif"] = GetRandomint(4);
- break;
- case "3":
- gif = CreateRandomCode(4);
- Session["gif"] = CreateRandomCode(4);
- break;
- default:
- gif = CreateRandomCode(4);
- Session["gif"] = CreateRandomCode(4);
- break;
- }
- CreateImage(Session["gif"].ToString());
- }
- private String GetRandomint(int codeCount)
- {
- Random random = new Random();
- string min = "";
- string max = "";
- for (int i = 0; i < codeCount; i++)
- {
- min +="1";
- max+="9";
- }
- return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());
- }
- /**/
- /*
- 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[] CreateRegionCode(int strlength)
- {
- //定义一个字符串数组储存汉字编码的组成元素
- string[] rBase = 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 = rBase[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 = rBase[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 = rBase[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 = rBase[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 string stxt(int num)
- {
- Encoding gb = Encoding.GetEncoding("gb2312");
- //调用函数产生10个随机中文汉字编码
- object[] bytes = CreateRegionCode(num);
- string strtxt = "";
- //根据汉字编码的字节数组解码出中文汉字
- for (int i = 0; i < num; i++)
- {
- strtxt += gb.GetString((byte[])Convert.ChangeType(bytes, typeof(byte[])));
- }
- return strtxt;
- }
- /// <summary>
- /// 这个是使用字母,数字混合
- /// </summary>
- /// <param name="VcodeNum"></param>
- /// <returns></returns>
- private string CreateRandomCode(int codeCount)
- {
- string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";
- string[] allCharArray = allChar.Split(',');
- string randomCode = "";
- int temp = -1;
- Random rand = new Random();
- for (int i = 0; i < codeCount; i++)
- {
- if (temp != -1)
- {
- rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
- }
- int t = rand.Next(61);
- if (temp == t)
- {
- return CreateRandomCode(codeCount);
- }
- temp = t;
- randomCode += allCharArray[t];
- }
- return randomCode;
- }
- private void CreateImage(string checkCode)
- {
- int iwidth = (int)(checkCode.Length * 20);
- System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 25);
- Graphics g = Graphics.FromImage(image);
- Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);
- Brush b = new System.Drawing.SolidBrush(Color.White);
- //g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
- g.Clear(Color.Black);
- g.DrawString(checkCode, f, b, 3, 3);
- Pen blackPen = new Pen(Color.Black, 0);
- Random rand = new Random();
- //for (int i=0;i<5;i++)
- //{
- // int y = rand.Next(image.Height);
- // g.DrawLine(blackPen,0,y,image.Width,y);
- //}
- System.IO.MemoryStream ms = new System.IO.MemoryStream();
- image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
- Response.ClearContent();
- Response.ContentType = "image/Jpeg";
- Response.BinaryWrite(ms.ToArray());
- g.Dispose();
- image.Dispose();
- }
- }
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四、效果图展示
验证码数字
附件: 2009012211325814.jpg
验证码数字+字母
附件: 2009012211340940.jpg
验证码汉字
附件: 2009012211350930.jpg