简单验证码的产生

 

// 1.建立ValidateCode.aspx页面cs代码

public   class  ValidateCode : System.Web.UI.Page
     {
        private void Page_Load(object sender, System.EventArgs e)
        {
            //如果要在页面a.aspx生成验证码，则在该页面添加一个图片控件，假设命名为：Image1，然后在page_Load事件中写如下代码：
            //ImageButton1.ImageUrl = "ValidateCode.aspx";
            //这样就可以生成验证码了，ValidateCode.aspx页面可以随便放在哪里，不过要注意Image1.src 要写对，同级可以直接写ValidateCode.aspx，上一级写../ValidateCode.aspx，很方便吧。

            if(!IsPostBack)
            {
                //RndNum是一个自定义函数
                //这里的数字4代表显示的是4位的验证字符串！
                //string VNum=RndNum(4); 
                string VNum=GenerateRandom(4);
                Session["VNum"] = VNum;
                Validate_Code(VNum);
            }
        }

        Web Form Designer generated codeWeb Form Designer generated code#region Web Form Designer generated code
        override protected void OnInit(EventArgs e)
        {
            //
            // CODEGEN: This call is required by the ASP.NET Web Form Designer.
            //
            InitializeComponent();
            base.OnInit(e);
        }
        
        /**//**//**//// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {    
            this.Load += new System.EventHandler(this.Page_Load);

        }
        #endregion

        private void Validate_Code(string VNum) 
        {
            int Gheight=(int)(VNum.Length * 11.5);
            //gheight为图片宽度,根据字符长度自动更改图片宽度
            System.Drawing.Bitmap Img = new System.Drawing.Bitmap(Gheight,20);
            Graphics g = Graphics.FromImage(Img);
            g.DrawString(VNum,new System.Drawing.Font("Arial",10),new System.Drawing.SolidBrush(Color.Red),3,3); 
            //在矩形内绘制字串（字串，字体，画笔颜色，左上x.左上y） 
            System.IO.MemoryStream ms=new System.IO.MemoryStream();
            Img.Save(ms,System.Drawing.Imaging.ImageFormat.Png); 
            Response.ClearContent(); //需要输出图象信息 要修改HTTP头 
            Response.ContentType="image/Png";
            Response.BinaryWrite(ms.ToArray());
            g.Dispose();
            Img.Dispose(); 
            Response.End();
        }
        
        private static char[] constant=
        {
            '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','v','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'
        };
        public static string GenerateRandom(int Length)
        {   
            System.Text.StringBuilder newRandom = new System.Text.StringBuilder(62);
            Random rd= new Random();
            for(int i=0;i<Length;i++)
            {
                newRandom.Append(constant[rd.Next(62)]);
            }
            return newRandom.ToString();
        }

    }

// 2.建立演示页面Login.aspx,html代码
< HTML >
     < HEAD >
         < title > Login </ title >
         < meta name = " GENERATOR "  Content = " Microsoft Visual Studio .NET 7.1 " >
         < meta name = " CODE_LANGUAGE "  Content = " C# " >
         < meta name = " vs_defaultClientScript "  content = " JavaScript " >
         < meta name = " vs_targetSchema "  content = " http://schemas.microsoft.com/intellisense/ie5 " >
     </ HEAD >
     < body >
         < form id = " Form1 "  method = " post "  runat = " server " >
             < table align = " center "  cellSpacing = " 0 "  cellPadding = " 0 "  width = " 100% "  border = " 0 "  height = " 100% " >
                 < colgroup >
                     < col width = " 30% " >
                     </ col >
                     < col width = " 40% " >
                     </ col >
                     < col width = " 30% " >
                     </ col >
                 </ colgroup >
                 < tr >
                     < td ></ td >
                     < td valign = " middle " >
                         < TABLE id = " Table1 "  align = " center "  cellSpacing = " 0 "  cellPadding = " 0 "  width = " 100% "  border = " 0 " >
                             < colgroup >
                                 < col width = " 20% " >
                                 </ col >
                                 < col width = " 35% " >
                                 </ col >
                                 < col width = " 25% " >
                                 </ col >
                                 < col width = " 20% " >
                                 </ col >
                             </ colgroup >
                             < TR >
                                 < TD align = " right " > LoginName </ TD >
                                 < TD >
                                     < asp:TextBox id = " txtLoginName "  runat = " server "  Width = " 100% " ></ asp:TextBox ></ TD >
                                 < td ></ td >
                                 < td ></ td >
                             </ TR >
                             < TR >
                                 < TD align = " right " > Password </ TD >
                                 < TD >
                                     < asp:TextBox id = " txtPassword "  runat = " server "  Width = " 100% " ></ asp:TextBox ></ TD >
                                 < td ></ td >
                                 < td ></ td >
                             </ TR >
                             < TR >
                                 < TD align = " right " > ValidateCode </ TD >
                                 < TD >
                                     < asp:TextBox id = " txtValidateCode "  runat = " server "  Width = " 100% " ></ asp:TextBox ></ TD >
                                 < td >< IMG alt = ""  src = " Pages/Wonderful/Form/ValidateCode.aspx " ></ td >
                                 < td ></ td >
                             </ TR >
                             < TR >
                                 < TD ></ TD >
                                 < TD >
                                     < asp:Button id = " Login "  runat = " server "  Text = " Login " ></ asp:Button >
                                     < asp:Button id = " Reset "  runat = " server "  Text = " Reset " ></ asp:Button ></ TD >
                                 < td ></ td >
                                 < td ></ td >
                             </ TR >
                         </ TABLE >
                     </ td >
                     < td ></ td >
                 </ tr >
             </ table >
         </ form >
     </ body >
</ HTML > 3 .Login页面的cs代码
public   class  Login : System.Web.UI.Page
{
    protected System.Web.UI.WebControls.TextBox txtLoginName;
    protected System.Web.UI.WebControls.TextBox txtPassword;
    protected System.Web.UI.WebControls.TextBox txtValidateCode;
    protected System.Web.UI.WebControls.Button Login;
    protected System.Web.UI.WebControls.Button Reset;
    protected System.Web.UI.WebControls.TextBox TextBox1;
private void Page_Load(object sender, System.EventArgs e)
        {
            if(Session["VNum"]!=null && Session["VNum"].ToString()==txtValidateCode.Text)
            {
                //验证码正确
            }
        }

        Web Form Designer generated codeWeb Form Designer generated code#region Web Form Designer generated code
        override protected void OnInit(EventArgs e)
        {
            //
            // CODEGEN: This call is required by the ASP.NET Web Form Designer.
            //
            InitializeComponent();
            base.OnInit(e);
        }
        
        /**//**//**//// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {    
            this.Load += new System.EventHandler(this.Page_Load);

        }
        #endregion

}