LoginForm.cs

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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using System.Data;
using System.Drawing;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace LoginFrame
{
    public partial class LoginForm : Form
    {
        //随机码的长度
        private const int iVerifyCodeLength = 4;
        //随机码
        private String strVerifyCode = "";
        public LoginForm()
        {
            InitializeComponent();
            UpdateVerifyCode();
        }
        private void UpdateVerifyCode()
        {
            strVerifyCode = CreateRandomCode(iVerifyCodeLength);
            CreateImage(strVerifyCode);
        }
        private string CreateRandomCode(int iLength)
        {
            int rand;
            char code;
            string randomCode = String.Empty;

            //生成一定长度的验证码
            System.Random random = new Random();
            for (int i = 0; i < iLength; i++)
            {
                rand = random.Next();
                code = (char)('0' + (char)(rand % 10));
                randomCode += code.ToString();
            }
            return randomCode;
        }
        /// 创建随机码图片
        private void CreateImage(string strVerifyCode)
        {
            try
            {
                int iRandAngle = 45; //随机转动角度
                int iMapWidth = (int)(strVerifyCode.Length * 21);
                Bitmap map = new Bitmap(iMapWidth, 28); //创建图片背景

                Graphics graph = Graphics.FromImage(map);
                graph.Clear(Color.AliceBlue);//清除画面，填充背景
                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