【C#】 如何实现文本框历史记录提示功能

        #region//提示历史记录功能
        DataTable dt = loginfa.SelectLogin_re();

        int n = dt.Rows.Count;//定义虚表数据数量

        string[] k = new string[n];//定义字符串数组
        var source = new AutoCompleteStringCollection();
        for (int i = 0; i < n; i++)//遍历增加数据
        {
            k[i] = dt.Rows[i][0].ToString();
            string a = k[i].ToString();
            source.AddRange(new string[]
                   {
                    a
                   });
            txtUserID.AutoCompleteCustomSource = source;
            txtUserID.AutoCompleteMode = AutoCompleteMode.SuggestAppend;
            txtUserID.AutoCompleteSource = AutoCompleteSource.CustomSource;
        }
        #endregion