C#中解决在STRING.SPLIT()中不能用字符串分割另一字符串的问题

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Text.RegularExpressions;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        string a = "a!?a!?a!?a";
        string b = "aa";
        string standard = "!?";
        //Regex reg;
        //string[] name = Regex.Split(a, @"\!\?", RegexOptions.IgnoreCase);
        string[] name = a.Split(standard.ToCharArray());
      //  int c = a.CompareTo((string)Session["name"]);
        //if (c == 0) Response.Write(c);
        //Response.Write(name.Length);
        for (int i = 0; i < name.Length; i++)
        {
            Response.Write(name[i]);
            Response.Write("<br>");
        }
    }
}