ASP.NET CRUD OPERATION

 using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;
using System.Web.Configuration;
public partial class _Default : System.Web.UI.Page
{
    private SqlConnection con;
    private void connection()
    {
        string constring = WebConfigurationManager.
            ConnectionStrings["connstring"].ToString();
        con = new SqlConnection(constring);
    }
    protected void Page_Load(object sender, EventArgs e)
    {
        if(!IsPostBack)
        {
            gvdisp();
        }
    }
    protected void btninsert_Click(object sender, EventArgs e)
    {
        try
        {
            connection();
            con.Open();
            bool rescheckrecord = CheckRecord(txtname.Text, txtcity.Text);
            if (rescheckrecord == false)
            {
                con.Close();
                Response.Write("<font color='red'>Record All Ready Exits</font><br/><hr/>");
                txtname.Text = "";
                txtcity.Text = "";
            }
            else
            {
                con.Open();
                SqlCommand cmd = new SqlCommand("sp_InsertRecord", con);
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@studname", txtname.Text);
                cmd.Parameters.AddWithValue("@studcity", txtcity.Text);
                int res = cmd.ExecuteNonQuery();
                if (res > 0)
                {
                    con.Close();
                    Response.Write("<script>alert('Insert Record Successfully');</script>");
                    txtname.Text = "";
                    txtcity.Text = "";
                    gvdisp();
                }
            }
        }
        catch (Exception ex)
        {
            con.Close();
            Response.Write("<script>alert(" + ex.Message + ");</script>");
        }
    }
    public bool CheckRecord(string nm, string city)
    {
        connection();
        con.Open();
        SqlCommand cmd = new SqlCommand("sp_GetSpecificRecord", con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.AddWithValue("@studname", nm);
        cmd.Parameters.AddWithValue("@studcity", city);
        SqlDataReader dr = cmd.ExecuteReader();
        if (dr.Read())
        {
            dr.Close();
            con.Close();
            return false;
        }
        else
        {
            dr.Close();
            con.Close();
            return true;
        }
    }
    public void gvdisp()
    {
        connection();
        con.Open();
        SqlCommand cmd = new SqlCommand("sp_GetAllRecord", con);
        cmd.CommandType = CommandType.StoredProcedure;
        SqlDataAdapter sda = new SqlDataAdapter(cmd);
        DataTable dt = new DataTable();
        sda.Fill(dt);
        con.Close();
        gvstudent.DataSource = dt;
        gvstudent.DataBind();

    }
    protected void OnRowEditing(object sender, GridViewEditEventArgs e)
    {
        gvstudent.EditIndex = e.NewEditIndex;
        gvdisp();
    }
    protected void OnRowCancelEdit(object sender, GridViewCancelEditEventArgs e)
    {
        gvstudent.EditIndex = -1;
        gvdisp();
    }
    protected void OnRowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        try
        {
           
            GridViewRow row = gvstudent.Rows[e.RowIndex];
            int id = Convert.ToInt16(gvstudent.DataKeys[e.RowIndex].Values[1]);
            string name = (row.Cells[2].Controls[0] as TextBox).Text;
            string city = (row.Cells[3].Controls[0] as TextBox).Text;
            connection();
            con.Open();
            SqlCommand cmd = new SqlCommand("sp_UpdateRecord", con);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@studid", id);
            cmd.Parameters.AddWithValue("@studname", name);
            cmd.Parameters.AddWithValue("@studcity", city);
            int res = cmd.ExecuteNonQuery();
            if (res > 0)
            {
                gvstudent.EditIndex = -1;
                con.Close();
                Response.Write("<script>alert('Record Update Successfully');</script>");
                gvdisp();
                
            }
        }
        catch (Exception ex)
        {
            Response.Write(ex.Message);
        }
    }
    protected void OnRowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        int id = Convert.ToInt16(gvstudent.DataKeys[e.RowIndex].Values[0]);
        connection();
        con.Open();
        SqlCommand cmd = new SqlCommand("sp_DeleteRecord", con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.AddWithValue("@studid", id);
        int res = cmd.ExecuteNonQuery();
        if (res > 0)
        {
            Response.Write("<script>alert('Record Delete Successfully');</script>");
            con.Close();
            gvdisp();
        }

    }
    protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow && e.Row.RowIndex != gvstudent.EditIndex)
        {
            (e.Row.Cells[0].Controls[2] as LinkButton).Attributes["onclick"] = "return confirm('Are you sure want to delete record?');";
        }
    }
}