textBox框像百度搜索出现下拉列表的样式，如图：

具体实现代码如下：

将此方法在frmLogin_Load事件里加载，

 private void bindTxt()        {            txtUser.AutoCompleteCustomSource = null;            User user = new User();            List
     
       userList = user.GetUserList();            if (userList.Count > 0)            {                foreach (UserInfo var in userList)                {                    txtUser.AutoCompleteCustomSource.Add(var.UserId);                }            }            txtUser.AutoCompleteMode = AutoCompleteMode.SuggestAppend;            txtUser.AutoCompleteSource = AutoCompleteSource.CustomSource;        }