Add,Update,Delete In Grid View

Create  Database Name as Inventory.
Create Table Name as Books Columns are Id (int),Title(nvarchar),ISBN(nvarchar),Price(Number).

Paste the Code on aspx Page:-

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"
    CodeBehind="Default.aspx.cs" Inherits="WebApplication1._Default" %>

<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
    <h2>
        Welcome to ASP.NET!
    </h2>
    <h2>
    <asp:Label ID="lblMsg" runat="server"  >  </asp:Label>
    </h2>

  <table>
  <tr>
  <td width="120px">
   <asp:Label ID="Label3" runat="server" Text="ID">  </asp:Label>
  </td>
  <td width="180px">
  <asp:TextBox runat="server" ID="txtId"></asp:TextBox>
  </td>
  </tr>
  <tr>
  <td width="120px">
   <asp:Label ID="Label1" runat="server" Text="Name">  </asp:Label>
  </td>
  <td width="180px">
   <asp:TextBox runat="server" ID="txtName"></asp:TextBox>
  </td>
  </tr>
   <tr>
  <td width="120px">
  <asp:Label ID="LblISBN" runat="server" Text="ISBN">  </asp:Label>
  </td>
  <td width="180px">
   <asp:TextBox runat="server" ID="txtISBN"></asp:TextBox>
  </td>
  </tr>
   <tr>
  <td width="120px">
  <asp:Label ID="Label2" runat="server" Text="Price">  </asp:Label>
  </td>
  <td width="180px">
   <asp:TextBox runat="server" ID="txtPrice"></asp:TextBox>
  </td>
  </tr>

  <tr>
  <td>
  <asp:Button ID="btnSubmit" runat="Server" Text="Submit" onclick="btnSubmit_Click" />
  </td>


  </tr>
  </table>
  <br />
  <asp:GridView ID="grdDetails" runat="server" Width="250px" AutoGenerateDeleteButton="True"
        AutoGenerateEditButton="True" CellPadding="4" ForeColor="#333333"
        GridLines="None" onrowcancelingedit="grdDetails_RowCancelingEdit"
        onrowdeleting="grdDetails_RowDeleting" onrowediting="grdDetails_RowEditing"
        onrowupdating="grdDetails_RowUpdating" onrowcanceling="grdDetails_RowCancelingEdit" >
      <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
      <EditRowStyle BackColor="#999999" />
      <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
      <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
      <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
      <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
      <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
      <SortedAscendingCellStyle BackColor="#E9E7E2" />
      <SortedAscendingHeaderStyle BackColor="#506C8C" />
      <SortedDescendingCellStyle BackColor="#FFFDF8" />
      <SortedDescendingHeaderStyle BackColor="#6F8DAE" />
    </asp:GridView>
 
</asp:Content>



=================================

Paste the Code ob aspx.cs Page:-
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;

namespace WebApplication1
{

    public partial class _Default : System.Web.UI.Page
    {
        //  Connection String
        // public const String ConnectionString = "server=.;database=Inventory;User                              Id=sa;password=sa123";

        SqlConnection Con = new SqlConnection(Settings.ConnectionString);

        protected void Page_Load(object sender, EventArgs e)
        {

            if (!IsPostBack)
            {
                grdDetails.DataSource = GetData();
                grdDetails.DataBind();

            }
        }
        DataTable GetData()
        {
            DataTable dt = new DataTable();
            {
                SqlConnection con = new SqlConnection(Settings.ConnectionString);
                con.Open();
                SqlCommand cmd = new SqlCommand("select * From Books ", con);
                SqlDataAdapter adpt = new SqlDataAdapter(cmd);
                adpt.Fill(dt);

            }
            return dt;
        }



        protected void btnSubmit_Click(object sender, EventArgs e)
        {
            SqlConnection Con = new SqlConnection(Settings.ConnectionString);
            Con.Open();
            string query = "insert into Books(ID,Title,ISBN,Price)Values('" + txtId.Text + "','" + txtName.Text + "','" + txtISBN.Text + "','" + txtPrice.Text + "' )";
            SqlCommand cmd = new SqlCommand(query, Con);
            cmd.ExecuteNonQuery();
            Con.Close();
            lblMsg.Text = "Saving is Done";
            txtId.Text = "";
            txtName.Text = "";
            txtISBN.Text = "";
            txtPrice.Text = "";
            Response.Redirect("default.aspx");

        }
   

        protected void grdDetails_RowEditing(object sender, GridViewEditEventArgs e)
        {
            grdDetails.EditIndex = e.NewEditIndex;
        }

        protected void grdDetails_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
        {
            grdDetails.EditIndex = -1;
            GetData();
        }


        protected void grdDetails_RowUpdating(object sender, GridViewUpdateEventArgs e)
        {
            GridViewRow row = grdDetails.Rows[grdDetails.EditIndex];
            int Id = int.Parse(((TextBox)row.Cells[1].Controls[0]).Text);
            // string Title = ((TextBox)row.Cells[2].Controls[0]).Text;
            TextBox txtTitle = (TextBox)row.Cells[2].Controls[0];
            TextBox txtISBN = (TextBox)row.Cells[3].Controls[0];
            TextBox txtPrice = (TextBox)row.Cells[4].Controls[0];
            Con.Open();
            SqlCommand cmd = new SqlCommand("update Books set Title='" + txtTitle.Text + "', ISBN='" + txtISBN.Text + "',Price='" + txtPrice.Text + "' where Id=" + Id, Con);
            cmd.ExecuteNonQuery();
            Con.Close();
            grdDetails.EditIndex = -1;
            GetData();
            Response.Redirect("Default.aspx");
            Response.Write("<Script>alert('Updated Successfully') </script>");
        }

        protected void grdDetails_RowDeleting(object sender, GridViewDeleteEventArgs e)
        {
            GridViewRow row = grdDetails.Rows[e.RowIndex];
            int Id = int.Parse(row.Cells[1].Text);
            Con.Open();
            SqlCommand cmd = new SqlCommand("delete from Books where Id=" + Id, Con);
            int result = cmd.ExecuteNonQuery();
            Con.Close();
            Response.Redirect("Default.aspx");
            Response.Write("<Script>alert('DeletedSuccessfully') </script>");
        }
    }

}

 For More details Follow the link     working with Grid View