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[4];
System.Security.Cryptography.RNGCryptoServiceProvider rng = new System.Security.Cryptography.RNGCryptoServiceProvider();
rng.GetBytes(bytes);
return BitConverter.ToInt32(bytes, 0);
}
public Form1()
{
InitializeComponent();


for (int i = 0; i < 20000000; 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());
}

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;

}


 面是2000W数据加载后的效果