C#WinForm 实现登录界面验证码功能（区分大小写+不区分大小写）

文章来自：https://blog.csdn.net/IT_xiao_guang_guang/article/details/104250015

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一、功能界面

图1 验证码(区分大小写)

图2 验证码(不区分大小写)

二、创建一个产生验证码的类Class1

（1）生成随机验证码字符串，用的是Random随机函数
（2）创建验证码图片，将该字符串画在PictureBox控件中

Class1.cs：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;//图片
using System.Windows.Forms;

namespace ValidCodeTest
{
    public class Class1
    {
        #region 验证码功能            
        /// <summary>
        /// 生成随机验证码字符串
        /// </summary>
        public static string CreateRandomCode(int CodeLength)  
        {
            int rand;
            char code;
            string randomCode = String.Empty;//随机验证码
            //生成一定长度的随机验证码
            Random random = new Random();
            for (int i = 0; i < CodeLength; i++)
            {
                rand = random.Next();
                if (rand % 3 == 1)
                {
                    code = (char)('A' + (char)(rand % 26));
                }
                else if (rand % 3 == 2)
                {
                    code = (char)('a' + (char)(rand % 26));                    
                }
                else
                {
                    code = (char)('0' + (char)(rand % 10));
                }
                randomCode += code.ToString();
            }
            return randomCode;
        }

        /// <summary>
        /// 创建验证码图片
        /// </summary>
        public static void CreateImage(string strValidCode, PictureBox pbox)
        {
            try
            {
                int RandAngle = 45;//随机转动角度
                int MapWidth = (int)(strValidCode.Length * 21);
                Bitmap map = new Bitmap(MapWidth, 28);//创建图片背景

                Graphics graph = Graphics.FromImage(map);
                graph.Clear(Color.AliceBlue);//清除绘画面,填充背景色
                graph.DrawRectangle(new Pen(Color.Black, 0), 0, 0, map.Width - 1, map.Height - 1);//画一个边框
                graph.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;//模式
                Random rand = new Random();
                //背景噪点生成
                Pen blackPen = new Pen(Color.LightGray, 0);
                for (int i = 0; i < 50; i++)
                {
                    int x = rand.Next(0, map.Width);
                    int y = rand.Next(0, map.Height);
                    graph.DrawRectangle(blackPen, x, y, 1, 1);
                }
                //验证码旋转，防止机器识别
                char[] chars = strValidCode.ToCharArray();//拆散字符串成单字符数组
                //文字居中
                StringFormat format = new StringFormat(StringFormatFlags.NoClip);
                format.Alignment = StringAlignment.Center;
                format.LineAlignment = StringAlignment.Center;
                //定义颜色
                Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
                //定义字体
                string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
                for (int i = 0; i < chars.Length; i++)
                {
                    int cindex = rand.Next(7);
                    int findex = rand.Next(5);
                    Font f = new System.Drawing.Font(font[findex], 13, System.Drawing.FontStyle.Bold);//字体样式(参数2为字体大小)
                    Brush b = new System.Drawing.SolidBrush(c[cindex]);
                    Point dot = new Point(16, 16);

                    float angle = rand.Next(-RandAngle, RandAngle);//转动的度数
                    graph.TranslateTransform(dot.X, dot.Y);//移动光标到指定位置
                    graph.RotateTransform(angle);
                    graph.DrawString(chars[i].ToString(), f, b, 1, 1, format);

                    graph.RotateTransform(-angle);//转回去
                    graph.TranslateTransform(2, -dot.Y);//移动光标到指定位置
                }
                pbox.Image = map;
            }
            catch (ArgumentException)
            {
                MessageBox.Show("验证码图片创建错误");
            }
        }
        #endregion
    }
}

---

三、调用

（1）更新验证码
（2）验证（区分大小写）
（3）验证（不区分大小写）

Form1.cs：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using ValidCodeTest;

namespace ValidCode
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }


        #region 验证码
        private const int ValidCodeLength = 4;//验证码长度        
        private String strValidCode = "";//验证码                        

        //调用自定义函数,更新验证码
        private void UpdateValidCode()
        {
            strValidCode = Class1.CreateRandomCode(ValidCodeLength);//生成随机验证码
            if (strValidCode == "") return;
            Class1.CreateImage(strValidCode, pbox1);//创建验证码图片
        }
        #endregion


        private void pbox1_Click(object sender, EventArgs e)
        {
            UpdateValidCode();//点击更新验证码
        }


        private void Form1_Load(object sender, EventArgs e)
        {
            UpdateValidCode();//加载更新验证码
        }


        /// <summary>
        ///  验证（区分大小写）
        /// </summary>        
        private void btn1_Click(object sender, EventArgs e)
        {
            string validcode = txtValidCode.Text.Trim();

            char[] ch1 = validcode.ToCharArray();
            char[] ch2 = strValidCode.ToCharArray();
            int Count1 = 0;//字母个数
            int Count2 = 0;//数字个数

            if (String.IsNullOrEmpty(validcode) != true)//验证码不为空
            {
                for (int i = 0; i < strValidCode.Length; i++)
                {
                    if ((ch1[i] >= 'a' && ch1[i] <= 'z') || (ch1[i] >= 'A' && ch1[i] <= 'Z'))//字母
                    {
                        if (ch1[i] == ch2[i])
                        {
                            Count1++;
                        }
                    }
                    else//数字
                    {
                        if (ch1[i] == ch2[i])
                        {
                            Count2++;
                        }
                    }

                }

                int CountSum = Count1 + Count2;
                if (CountSum == strValidCode.Length)
                {
                    MessageBox.Show("验证通过", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    UpdateValidCode();
                    txtValidCode.Text = "";
                    txtValidCode.Focus();
                }
                else
                {
                    MessageBox.Show("验证失败", "警告", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                    UpdateValidCode();//更新验证码
                    txtValidCode.Text = "";
                    txtValidCode.Focus();
                }
            }
            else//验证码为空
            {
                MessageBox.Show("请输入验证码", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
                UpdateValidCode();//更新验证码
                txtValidCode.Text = "";
                txtValidCode.Focus();
            }
        }


        /// <summary>
        ///  验证（不区分大小写）
        /// </summary>  
        private void btn2_Click(object sender, EventArgs e)
        {
            string validcode = txtValidCode.Text.Trim();

            if (String.IsNullOrEmpty(validcode) != true)//验证码不为空
            {
                if (validcode.ToLower() == strValidCode.ToLower())
                {
                    MessageBox.Show("验证通过", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    UpdateValidCode();
                    txtValidCode.Text = "";
                    txtValidCode.Focus();
                }
                else
                {
                    MessageBox.Show("验证失败", "警告", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                    UpdateValidCode();//更新验证码
                    txtValidCode.Text = "";
                    txtValidCode.Focus();
                }
            }
            else//验证码为空
            {
                MessageBox.Show("请输入验证码", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
                UpdateValidCode();//更新验证码
                txtValidCode.Text = "";
                txtValidCode.Focus();
            }
        }
    }
}

  .exe测试文件下载地址: https://www.lanzous.com/i984xva
  密码：test