C语言实现数据结构中删除字符串操作

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;

namespace WebApplication1
{
    public partial class Add_kaoshi_timu2 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            string sstr1 = Session["drop1"].ToString();
            string sstr2 = Session["drop2"].ToString();
            string sstr3 = Session["drop3"].ToString();
            if (DropDownList1.SelectedItem.Value == "1")
            {
                DB db = new DB();

                SqlConnection con = db.createConnection();
                con.Open();
                string cmdstr = "insert into Test_Questions (Que_professionid,Que_lessionid,Que_taotiid,Que_subject,Que_type,OptionA,OptionB,OptionC,OptionD,Que_answer,note )values('" + sstr1 + "','" + sstr2 + "','" + sstr3 + "','" + TextBox1.Text + "','" + DropDownList1.SelectedItem.Text + "','" + this.TextBox2.Text + "','" + this.TextBox3.Text + "','" + this.TextBox4.Text + "','" + this.TextBox5.Text + "','" + DropDownList2.Text + "','" + this.TextBox6.Text + "')";
                SqlCommand cmd = new SqlCommand(cmdstr, con);
                cmd.Dispose();
                try
                {
                    cmd.ExecuteNonQuery();
                    Response.Write("<script>alert('增加成功!');</script>");



                }
                catch (SqlException)
                {
                    Response.Write("<script>alert('增加失败!');</script>");
                }
                finally
                {
                    con.Close();

                }
            }

            else
            {
                if (CheckBox1.Checked == true && CheckBox2.Checked == true && CheckBox3.Checked == true && CheckBox4.Checked == true)
                {
                    string str1 = "A,B,C,D";
                    DB db = new DB();