str.split()如何用?谢谢

string Val = DropDownList1.SelectedValue;
        string[] arr=Val.Split('|');
        string RedirectUrl="ProSearch.aspx?BigClassID="+arr[0];
        if(Convert.ToInt32(arr[1])>0)
            RedirectUrl+="&SmallClassID="+arr[1];
        RedirectUrl+="&KeyWord="+TextBox1.Text.Trim();
        Response.Redirect(RedirectUrl);