ASP. Net generate verification code

One . explain

This article is Xiaobai learning Morni Chang Teacher's video teaching <<Asp.Net WEB Server programming technology >> Study notes made in , Some knowledge points follow the tutorial , You can also go to the teacher's homepage to learn , Thank you. .

Two . Generate captcha image (checkcode.aspx.cs)

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace MyMusci
{
    
	public partial class checkcode : System.Web.UI.Page
	{
    
	    protected void Page_Load(object sender, EventArgs e)
	    {
    
	        string chkCode = string.Empty;
	        int ix, iy;
	        ix = 80;
	        iy = 24;
	        // Color list , Used for verification code 、 Noise line 、 noise  
	        Color[] color = {
     Color.Black, Color.Red, Color.Blue, Color.Green, Color.Orange, Color.Brown, Color.Brown, Color.DarkBlue };
	        // Font list , Used for verification code  
	        string[] font = {
     "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh", "MingLiU", "Arial" };
	        // The character set of the captcha , Removed some confusing characters  
	        char[] character = {
     '2', '3', '4', '5', '6', '8', '9','0','1',' One ',' Small ',' white ' };
	        Random rnd = new Random();
	        // Generate captcha string  
	        for (int i = 0; i < 4; i++)
	        {
    
	            chkCode += character[rnd.Next(character.Length)];
	        }
	        Bitmap bmp = new Bitmap(ix, iy);
	        Graphics g = Graphics.FromImage(bmp);
	        g.Clear(Color.White);
	        // Draw a noise line  
	        for (int i = 0; i < 10; i++)
	        {
    
	            int x1 = rnd.Next(ix);
	            int y1 = rnd.Next(iy);
	            int x2 = rnd.Next(ix);
	            int y2 = rnd.Next(iy);
	            Color clr = color[rnd.Next(color.Length)];
	            g.DrawLine(new Pen(clr), x1, y1, x2, y2);
	        }
	        // Draw the verification code string  
	        for (int i = 0; i < chkCode.Length; i++)
	        {
    
	            string fnt = font[rnd.Next(font.Length)];
	            Font ft = new Font(fnt, 14, FontStyle.Bold);
	            Color clr = color[rnd.Next(color.Length)];
	            g.DrawString(chkCode[i].ToString(), ft, new SolidBrush(clr), (float)i * 16 + 2, (float)2);
	        }
	        // Painting noise  
	        for (int i = 0; i < 50; i++)
	        {
    
	            int x = rnd.Next(bmp.Width);
	            int y = rnd.Next(bmp.Height);
	            Color clr = color[rnd.Next(color.Length)];
	            bmp.SetPixel(x, y, clr);
	        }
	        // Write the verification code to SESSION, Why can't the second page get the value ？？？
	        // General handler adds interface file ;
	        Session["Code"] = chkCode.ToUpper();
	        // Clear the page output cache , Set this page to have no cache  
	        Response.Buffer = true;
	        Response.ExpiresAbsolute = System.DateTime.Now.AddMilliseconds(0);
	        Response.Expires = 0;
	        Response.CacheControl = "no-cache";
	        Response.AppendHeader("Pragma", "No-Cache");
	        // Write the verification code image to the memory stream , And put it in  "image/Png"  Format output  
	        // My page returns pictures ;
	        MemoryStream ms = new MemoryStream();
	        try
	        {
    
	            bmp.Save(ms, ImageFormat.Png);
	            Response.ClearContent();
	            Response.ContentType = "image/Png";
	            Response.BinaryWrite(ms.ToArray());
	        }
	        finally
	        {
    
	            // Explicitly release resources  
	            bmp.Dispose();
	            g.Dispose();
	        }
	
	    }
	}
}	

3、 ... and . Add verification code to the login page (login_new.aspx)

stay table Add the following code to

<tr>
    <td>
         Verification Code </td>
    <td>
        <asp:TextBox ID="code" runat="server"></asp:TextBox>
    </td>
    <td><img id="imgcode" src="checkcode.aspx" /></td>
</tr>
<tr>
    <td>
        <asp:Button ID="btn_sub" runat="server" class="btn btn-primary" OnClick="btn_sub_Click" Text=" Sign in " />
    </td>
    <td>
    	<%-- The reset button is replaced here with register (LinkButton) Control 
    	PostBackUrl  Indicates the jump position of the control after clicking 
    	CausesValidation="False"  Indicates that you can jump to the position without validating the control 
    	--%>
        <asp:LinkButton ID="LinkButton1" runat="server" class="btn btn-secondary" PostBackUrl="~/RegUser.aspx" CausesValidation="False"> register </asp:LinkButton>
    </td>
    <td>&nbsp;</td>
</tr>

Join in jquery.js, And add the following script :

<script> // Picture click event  $("#imgcode").click(function () {
       $("#imgcode").attr("src", "checkcode.aspx?t=" + Math.random()); }) </script>

Every time we click on an image , Will refresh the contents of the picture , That is, the content of the verification code :