How do I delete and add new records in gridview in asp.net?

OnRowEditing="GridView1_RowEditing" OnRowUpdating="GridView1_RowUpdating">

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.Configuration;

using System.Data;

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

{

//Connection String from web.config File

string cs = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;

SqlConnection con;

SqlDataAdapter adapt;

DataTable dt;

protected void Page_Load(object sender, EventArgs e)

{

try

{

if (!IsPostBack)

{

ShowData();

}

}catch(Exception ex)

{

label12.Text = ex.Message;

}

}

//ShowData method for Displaying Data in Gridview

protected void ShowData()

{

dt = new DataTable();

con = new SqlConnection(cs);

con.Open();

adapt = new SqlDataAdapter("Select EXAM_Id,EXAM_TITLE,EXAM_DATE,TOTAL_TIME,GENERATED_EXAM_PAPER from EXAM_PAPER", con);

adapt.Fill(dt);

if (dt.Rows.Count > 0)

{

GridView1.DataSource = dt;

GridView1.DataBind();

}

con.Close();

}

protected void GridView1_RowEditing(object sender, System.Web.UI.WebControls.GridViewEditEventArgs e)

{

//NewEditIndex property used to determine the index of the row being edited.

GridView1.EditIndex = e.NewEditIndex;

ShowData();

}

protected void GridView1_RowUpdating(object sender, System.Web.UI.WebControls.GridViewUpdateEventArgs e)

{

//Finding the controls from Gridview for the row which is going to update

Label id = GridView1.Rows[e.RowIndex].FindControl("lbl_ID") as Label;

TextBox title = GridView1.Rows[e.RowIndex].FindControl("txt_title") as TextBox;

TextBox date = GridView1.Rows[e.RowIndex].FindControl("txt_date") as TextBox;

TextBox time = GridView1.Rows[e.RowIndex].FindControl("txt_time") as TextBox;

TextBox paper = GridView1.Rows[e.RowIndex].FindControl("txt_paper") as TextBox;

con = new SqlConnection(cs);

con.Open();

//updating the record

SqlCommand cmd = new SqlCommand("Update EXAM_PAPER set EXAM_TITLE='" + title.Text + "',EXAM_DATE='" + date.Text + "',TOTAL_TIME='" + time.Text + "',GENERATED_EXAM_PAPER='" + paper.Text + "' where EXAM_Id=" + Convert.ToInt32(id.Text), con);

cmd.ExecuteNonQuery();

con.Close();

//Setting the EditIndex property to -1 to cancel the Edit mode in Gridview

GridView1.EditIndex = -1;

//Call ShowData method for displaying updated data

ShowData();

}

protected void GridView1_RowCancelingEdit(object sender, System.Web.UI.WebControls.GridViewCancelEditEventArgs e)

{

//Setting the EditIndex property to -1 to cancel the Edit mode in Gridview

GridView1.EditIndex = -1;

ShowData();

}

}