Detailed explanation of how to generate ASP.NET verification code

General verification code generation methods are the same, the main steps are two steps

The first step: Randomly generate the numbers or letters of the system verification code, and by the way, add the randomly generated numbers or letters Write to Cookies or Session.

Step 2: Use the numbers or letters randomly generated in the first step to synthesize the picture.

It can be seen that the complexity of the verification code is mainly completed in the second step. You can set it according to the complexity you want.

Let’s take a look:

Step 1: How to randomly generate numbers or letters

/// 

  /// 生成验证码的随机数
  /// 
  /// 返回五位随机数
  private string GenerateCheckCode()
  {
    int number;
    char code;
    string checkCode = String.Empty;
 
    Random random = new Random();
 
    for (int i = 0; i < 5; i++)//可以任意设定生成验证码的位数
    {
      number = random.Next();
 
      if (number % 2 == 0)
        code = (char)('0' + (char)(number % 10));
      else
        code = (char)('A' + (char)(number % 26));
 
      checkCode += code.ToString();
    }
 
    Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));//写入COOKIS
    Session["CheckCode"] = checkCode; //写入Session，可以任意选一下
    return checkCode;
  }

Step 2: Generate pictures

/// 

  /// 生成验证码图片
  /// 
  /// 
  private void CreateCheckCodeImage(string checkCode)
  {
    if (checkCode == null || checkCode.Trim() == String.Empty)
      return;
 
    Bitmap image = new Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 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 < 25; i++)
      {
        int x1 = random.Next(image.Width);
        int x2 = random.Next(image.Width);
        int y1 = random.Next(image.Height);
        int y2 = random.Next(image.Height);
 
        g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
      }
 
      Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
      LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
      g.DrawString(checkCode, font, brush, 2, 2);
 
      //画图片的前景噪音点
      for (int i = 0; i < 100; i++)
      {
        int x = random.Next(image.Width);
        int y = random.Next(image.Height);
 
        image.SetPixel(x, 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);
 
      MemoryStream ms = new MemoryStream();
      image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
      Response.ClearContent();
      Response.ContentType = "image/Gif";
      Response.BinaryWrite(ms.ToArray());
    }
    finally
    {//释放对象资源
      g.Dispose();
      image.Dispose();
    }

* Complete program

First add a checkCode.aspx file to the project in VS2005, and add the following complete code to the checkCode.aspx.cs code file

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;
using System.IO;
using System.Drawing.Drawing2D;
 
public partial class checkCode : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {
    CreateCheckCodeImage(GenerateCheckCode());//调用下面两个方法;
  }
 
  /// 

  /// 生成验证码的随机数
  /// 
  /// 返回五位随机数
  private string GenerateCheckCode()
  {
    int number;
    char code;
    string checkCode = String.Empty;
 
    Random random = new Random();
 
    for (int i = 0; i < 5; i++)//可以任意设定生成验证码的位数
    {
      number = random.Next();
 
      if (number % 2 == 0)
        code = (char)('0' + (char)(number % 10));
      else
        code = (char)('A' + (char)(number % 26));
 
      checkCode += code.ToString();
    }
 
    Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));//写入COOKIS
    Session["CheckCode"] = checkCode; //写入Session，可以任意选一下
    return checkCode;
  }
 
 
  /// 

  /// 生成验证码图片
  /// 
  /// 
  private void CreateCheckCodeImage(string checkCode)
  {
    if (checkCode == null || checkCode.Trim() == String.Empty)
      return;
 
    Bitmap image = new Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 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 < 25; i++)
      {
        int x1 = random.Next(image.Width);
        int x2 = random.Next(image.Width);
        int y1 = random.Next(image.Height);
        int y2 = random.Next(image.Height);
 
        g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
      }
 
      Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
      LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
      g.DrawString(checkCode, font, brush, 2, 2);
 
      //画图片的前景噪音点
      for (int i = 0; i < 100; i++)
      {
        int x = random.Next(image.Width);
        int y = random.Next(image.Height);
 
        image.SetPixel(x, 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);
 
      MemoryStream ms = new MemoryStream();
      image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
      Response.ClearContent();
      Response.ContentType = "image/Gif";
      Response.BinaryWrite(ms.ToArray());
    }
    finally
    {//释放对象资源
      g.Dispose();
      image.Dispose();
    }
  }
 
}

Do all the above pages that generate verification codes Okay, let's call it and see:

Add the Image control where you need to use the verification code

404135e365a66f55c9bd993f7b536ff0

The verification code will be displayed on the Image control!

The display is done, of course we need to judge whether the user's input is correct!

As long as we get the value entered by the user and compare it with Cookies or Session, it will be OK

Get the value of Cookies Request.Cookies["CheckCode"].Value

Get the value of Session Value Session["CheckCode"].ToString()　(It is best to first determine whether the Session is empty)

If you do not want to be case sensitive, convert the values ​​entered by the user and the values ​​of Cookies or Session into uppercase or All lowercase

With usage

protected void Button1_Click(object sender, EventArgs e)
  {
    if (Request.Cookies["CheckCode"].Value == TextBox1.Text.Trim().ToString())
    {
      Response.Write("Cookies is right");
    }
    else
    {
      Response.Write("Cookies is wrong");
    }
 
    if (Session["CheckCode"] != null)
    {
      if (Session["CheckCode"].ToString().ToUpper() == TextBox1.Text.Trim().ToString().ToUpper())
        //这样写可以不能区分大小写
      {
        Response.Write("Session is right");
 
      }
      else
      {
        Response.Write("Session is wrong");
      }
    }
  }

The above is the entire content of this article, teaching you how to make ASP.NET verification code, I hope you like it.

For more detailed articles on how to generate ASP.NET verification codes, please pay attention to the PHP Chinese website!