Split and Replace Functions Asp.net C#

public partial class ReplaceSplit : System.Web.UI.Page

{

    Cls_ADO obj = new Cls_ADO();

    static int flag, idno;

    protected void Page_Load(object sender, EventArgs e)

    {

        if(!Page.IsPostBack)

        {

            fillDOB();

            fillSqn();

        }

    }

    protected void btnSave_Click(object sender, EventArgs e)

    {

        string name = txtuname.Text;

        string birth=ddlDD.Text+"/"+ddlMM.Text+"/"+ddlYY.Text;

        string squet = ddlQn.SelectedValue;

 squet = squet.Replace("'", "$");  /* here '  repalce with $ , because ' split the query , eg: squet = squet.Replace("'", "’’");*/

        if (flag == 1)

        {

            string upqry = "update tbl_reg set uname='" + name + "',dob='" + birth + "',sqn='" + squet + "' where uid=" + idno + "";

            obj.execute_Query(upqry);

            flag = 0;

        }

        else

        {

            string inqry = "insert into tbl_reg(uname,dob,sqn)values('" + name + "','" + birth + "','" + squet + "')";

            obj.execute_Query(inqry);

        }

       

        string selqry = "select * from tbl_reg";

        obj.fillGrid(grdDetails, selqry);

    }

protected void  btnShow_Click(object sender, EventArgs e)

{

    string selqry="select * from tbl_reg";

    obj.fillGrid(grdDetails, selqry);

}

    protected void fillDOB()

    {

        int i;

        for (i = 1; i <= 31; i++)

        {

            ddlDD.Items.Add(i.ToString());

        }

        for (i = 1; i <= 12; i++)

        {

            ddlMM.Items.Add(i.ToString());

        }

        for (i = 1990; i <= 2000; i++)

        {

            ddlYY.Items.Add(i.ToString());

        }

    }

    protected void fillSqn()

    {

        ddlQn.Items.Insert(0, "--select--");

        ddlQn.Items.Add("U r pet's name ?");

        ddlQn.Items.Add("Favourite Color ?");

   

       

    }

    protected void grdDetails_RowCommand(object sender, GridViewCommandEventArgs e)

    {

        if (e.CommandName == "editme")

        {

            

            flag = 1;

            idno = Convert.ToInt32(e.CommandArgument.ToString());

            string str = "select * from tbl_reg where uid=" + idno + "";

            DataTable dt = obj.select_Query(str);

            if (dt != null)

            {

                txtuname.Text = dt.Rows[0]["uname"].ToString();

               

          string squet = dt.Rows[0]["sqn"].ToString();

     

ddlQn.SelectedValue = squet.Replace("$", "'"); // here $ repalce with '

                string[] s1 = new string[3];

                string brth = dt.Rows[0]["dob"].ToString();

                 s1 = brth.Split('/'); // here split the string based on /

                ddlDD.SelectedValue = s1[0];

                ddlMM.SelectedValue = s1[1];

                ddlYY.SelectedValue = s1[2];

            }

        }

    }

}