c# 与数据库相连后 如何实现用户注册的功能

using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Collections;
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 blog.util;

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

    }
    protected void button_jcyh(object sender, EventArgs e)
    {
        string str = hy_count.Text;
        string sqlstr = "select count(*) from hy where hy_count="+str+"";
        Response.Write(sqlstr);
        int myread = Convert.ToInt32( DataPublic.ExecuteScalar(sqlstr));
        if (myread==0)
        {
            //Response.Write("帐号已存在，请重写帐号名！");
            Response.Write("<script>alert(\"帐号已存在，请重写帐号名！！\");</script>");
        }
        else