winform Textbox像百度一下实现下拉显示

 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;

 namespace _04TextBox
 {
     public partial class Form1 : Form
     {
         List<string> Data = new List<string>();

         string Randomstr = "功夫撒黑胡椒hcbvf蜂窝qwertyuiopasdfghjklzxcvbnm法国的恢复到飞范德萨QWERTYUIOPASDFGHJKLZXCVBNM出现过热423贴①46546也有一头热刚恢复到贴3天赋如头3广泛的我让他";

         Random rd = new Random(GetRandomSeed());

         static int GetRandomSeed()
         {
             byte[] bytes = new byte[];
             System.Security.Cryptography.RNGCryptoServiceProvider rng = new System.Security.Cryptography.RNGCryptoServiceProvider();
             rng.GetBytes(bytes);
             return BitConverter.ToInt32(bytes, );
         }

         public Form1()
         {
             InitializeComponent();

             //2000W数据，这里会有卡顿现象，这里修改为200W
             for (int i = ; i < ; i++)
             {
                 Data.Add(Randomstr.ToCharArray()[rd.Next(Randomstr.Length)].ToString()
                     + Randomstr.ToCharArray()[rd.Next(Randomstr.Length)].ToString()
                     + Randomstr.ToCharArray()[rd.Next(Randomstr.Length)].ToString()
                     + Randomstr.ToCharArray()[rd.Next(Randomstr.Length)].ToString()
                     + Randomstr.ToCharArray()[rd.Next(Randomstr.Length)].ToString());
             }
             //重点代码
             this.textBox1.AutoCompleteCustomSource.Clear();
             this.textBox1.AutoCompleteCustomSource.AddRange(Data.ToArray());
             this.textBox1.AutoCompleteMode = System.Windows.Forms.AutoCompleteMode.SuggestAppend;
             this.textBox1.AutoCompleteSource = System.Windows.Forms.AutoCompleteSource.CustomSource;
         }

         private void Form1_Load(object sender, EventArgs e)
         {

         }

     }
 }

Form1 TextBox Source Code

最终实现效果如下：