验证码的实现，及窗体抖动

验证码的实现，及窗体抖动

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1（）
        {
            InitializeComponent（）;
        }
        private void button2_Click（object sender EventArgs e）
        {
             string ai = ““;
            Random p = new Random（）;
            for （int i = 0; i < 4; i++）
            {
                int type = p.Next（0 3）;
                if （type ==0）
                {
                    ai += （（char）p.Next（97 123））.ToString（）;
                   // this.BackColor = Color.Red;
    

 属性            大小     日期    时间   名称
----------- ---------  ---------- -----  ----
     目录           0  2020-06-18 16:22  WindowsFormsApplication1\
     目录           0  2020-06-18 16:23  WindowsFormsApplication1\WindowsFormsApplication1\
     文件        6396  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\Form1.Designer.cs
     文件        5582  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\Form1.cs
     文件        6011  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\Form1.resx
     文件         505  2020-06-18 16:22  WindowsFormsApplication1\WindowsFormsApplication1\Program.cs
     目录           0  2020-06-18 16:22  WindowsFormsApplication1\WindowsFormsApplication1\Properties\
     文件        1380  2020-06-18 16:22  WindowsFormsApplication1\WindowsFormsApplication1\Properties\AssemblyInfo.cs
     文件        2900  2020-06-18 16:22  WindowsFormsApplication1\WindowsFormsApplication1\Properties\Resources.Designer.cs
     文件        5612  2020-06-18 16:22  WindowsFormsApplication1\WindowsFormsApplication1\Properties\Resources.resx
     文件        1111  2020-06-18 16:22  WindowsFormsApplication1\WindowsFormsApplication1\Properties\Settings.Designer.cs
     文件         249  2020-06-18 16:22  WindowsFormsApplication1\WindowsFormsApplication1\Properties\Settings.settings
     文件        3707  2020-06-18 16:24  WindowsFormsApplication1\WindowsFormsApplication1\WindowsFormsApplication1.csproj
     目录           0  2020-06-18 16:22  WindowsFormsApplication1\WindowsFormsApplication1\bin\
     目录           0  2020-06-18 16:24  WindowsFormsApplication1\WindowsFormsApplication1\bin\Debug\
     文件       12288  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\bin\Debug\WindowsFormsApplication1.exe
     文件       30208  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\bin\Debug\WindowsFormsApplication1.pdb
     文件       11600  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\bin\Debug\WindowsFormsApplication1.vshost.exe
     文件         490  2019-03-19 12:46  WindowsFormsApplication1\WindowsFormsApplication1\bin\Debug\WindowsFormsApplication1.vshost.exe.manifest
     目录           0  2020-06-18 16:22  WindowsFormsApplication1\WindowsFormsApplication1\obj\
     目录           0  2020-06-18 16:22  WindowsFormsApplication1\WindowsFormsApplication1\obj\x86\
     目录           0  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\obj\x86\Debug\
     文件        5420  2020-06-18 20:58  WindowsFormsApplication1\WindowsFormsApplication1\obj\x86\Debug\DesignTimeResolveAssemblyReferences.cache
     文件        6408  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\obj\x86\Debug\DesignTimeResolveAssemblyReferencesInput.cache
     目录           0  2020-06-19 09:20  WindowsFormsApplication1\WindowsFormsApplication1\obj\x86\Debug\TempPE\
     文件         180  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\obj\x86\Debug\WindowsFormsApplication1.Form1.resources
     文件         180  2020-06-18 16:24  WindowsFormsApplication1\WindowsFormsApplication1\obj\x86\Debug\WindowsFormsApplication1.Properties.Resources.resources
     文件        1026  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\obj\x86\Debug\WindowsFormsApplication1.csproj.FileListAbsolute.txt
     文件         975  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\obj\x86\Debug\WindowsFormsApplication1.csproj.GenerateResource.Cache
     文件        9174  2020-06-18 20:59  WindowsFormsApplication1\WindowsFormsApplication1\obj\x86\Debug\WindowsFormsApplication1.csprojResolveAssemblyReference.cache
     文件       12288  2020-06-19 09:17  WindowsFormsApplication1\WindowsFormsApplication1\obj\x86\Debug\WindowsFormsApplication1.exe
............此处省略3个文件信息