how to retrive data from aspx page ??

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>





   


   

   

            DataKeyNames="VendorId"
        AllowPaging="True"
        CellPadding="3"
        OnPageIndexChanging="ResultGridView_PageIndexChanging"
        OnRowDeleting="ResultGridView_RowDeleting"
        OnRowEditing="ResultGridView_RowEditing"
            OnRowUpdating="ResultGridView_RowUpdating"
            OnRowCancelingEdit="ResultGridView_RowCancelingEdit" PageSize="5"
            BackColor="#DEBA84" BorderColor="#DEBA84" BorderStyle="None" BorderWidth="1px"
            CellSpacing="2" OnRowCommand="ResultGridView_RowCommand" AllowSorting="true"
            onsorting="ResultGridView_Sorting">
           
                                    ReadOnly="True" SortExpression="VendorId" />
               
                   
                       
                   
                   
                   
                   
                   
                       
                   
               
               
                   
                       
                   
                   
                   
                   
                   
                       
                   
               
               
                   
                       
                   
                   
                   
                   
                   
                       
                   
               
               
                   
                       
                   
                   
                   
                   
                   
                       
                   
               
               
                   
                       
                   
                   
                   
                   
                   
                       
                   
               
               
                   
                       
                   
                   
                   
                   
                   
                       
                   
               
               
               
               
               
               
               
                 
                 
               
               
                 
               
               
                 
               
               
               
               

           
           
           
           
           
           
       



       
   
   
   
            onclick="btn_search_Click" />
   

   
   

   






using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;
public partial class _Default : System.Web.UI.Page
{
    string connStr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
    //SqlConnection conn = new SqlConnection(connStr);
    SqlDataAdapter ad = new SqlDataAdapter();
    SqlCommand cmd = new SqlCommand();
    DataTable dataTable;
    SqlDataAdapter sqlda;
    DataSet ds;
    string str;
    protected void Page_Load(object sender, EventArgs e)
    {
        Session["sortBy"] = null;
        if (!IsPostBack)
        {
            FillVendorGrid();
        }
    }
    private void FillVendorGrid()
    {
        SqlConnection conn = new SqlConnection(connStr);
        dataTable = new DataTable();
        cmd.Connection = conn;
        cmd.CommandText = "SELECT * FROM Vendor";
        ad = new SqlDataAdapter(cmd);
        ad.Fill(dataTable);
        ResultGridView.DataSource = dataTable;
        ResultGridView.DataBind();
       
    }

    protected void ResultGridView_RowEditing(object sender, GridViewEditEventArgs e)
    {
        ResultGridView.EditIndex = e.NewEditIndex;
        FillVendorGrid();
    }


    protected void ResultGridView_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        ResultGridView.PageIndex = e.NewPageIndex;
        FillVendorGrid();
    }

    protected void ResultGridView_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        SqlConnection conn = new SqlConnection(connStr);
        cmd.Connection = conn;
        cmd.CommandText = "DELETE FROM Vendor WHERE VendorId='" + ResultGridView.DataKeys[e.RowIndex].Values[0].ToString() + "'";
        conn.Open();
        cmd.ExecuteNonQuery();
        conn.Close();
        FillVendorGrid();

    }

    protected void ResultGridView_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        TextBox txtFName = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtFName");
        TextBox txtLName = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtLName");
        TextBox txtCity = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtCity");
        TextBox txtState = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtState");
        TextBox txtCountry = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtCountry");
        TextBox txtDescription = (TextBox)ResultGridView.Rows[e.RowIndex].FindControl("txtDescription");

        SqlConnection conn = new SqlConnection(connStr);
        cmd.Connection = conn;
        cmd.CommandText = "UPDATE Vendor SET VendorFName ='" + txtFName.Text + "',VendorLName ='" + txtLName.Text + "',VendorCity ='" + txtCity.Text + "',VendorState ='" + txtState.Text + "',VendorCountry ='" + txtCountry.Text + "',VendorDescription ='" + txtDescription.Text + "'   WHERE VendorId='" + ResultGridView.DataKeys[e.RowIndex].Values[0].ToString() + "'";
        conn.Open();
        cmd.ExecuteNonQuery();
        ResultGridView.EditIndex = -1;
        FillVendorGrid();
        conn.Close();

    }

    protected void ResultGridView_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
    {
        ResultGridView.EditIndex = -1;
        FillVendorGrid();

    }

    protected void ResultGridView_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName.Equals("AddNew"))
        {

            TextBox txtFName = (TextBox)ResultGridView.FooterRow.FindControl("txtFName1");
            TextBox txtLName = (TextBox)ResultGridView.FooterRow.FindControl("txtLName1");
            TextBox txtCity = (TextBox)ResultGridView.FooterRow.FindControl("txtCity1");
            TextBox txtState = (TextBox)ResultGridView.FooterRow.FindControl("txtState1");
            TextBox txtCountry = (TextBox)ResultGridView.FooterRow.FindControl("txtCountry1");
            TextBox txtDescription = (TextBox)ResultGridView.FooterRow.FindControl("txtDescription1");
            SqlConnection conn = new SqlConnection(connStr);
            cmd.Connection = conn;
            cmd.CommandText = "INSERT INTO Vendor(VendorFName, VendorLName,VendorCity,VendorState,VendorCountry,VendorDescription) Values('" + txtFName.Text + "', '" + txtLName.Text + "', '" + txtCity.Text + "', '" + txtState.Text + "', '" + txtCountry.Text + "' , '" + txtDescription.Text + "')";
            conn.Open();
            cmd.ExecuteNonQuery();
            FillVendorGrid();
            conn.Close();
        }
    }
    protected void btn_search_Click(object sender, EventArgs e)
    {
        SqlConnection conn = new SqlConnection(connStr);
        conn.Open();
        str = "select * from Vendor where VendorFName like '" + TextBox1.Text + "%'";
        cmd = new SqlCommand(str, conn);
        sqlda = new SqlDataAdapter(cmd);
        ds = new DataSet();
        sqlda.Fill(ds, "Vendor");
        conn.Close();
       

        ResultGridView.DataSource = ds;
        ResultGridView.DataMember = "Vendor";
        ResultGridView.DataBind();

    }
    protected void ResultGridView_Sorting(object sender, GridViewSortEventArgs e)
    {
        Session["sortBy"] = e.SortExpression;
        FillVendorGrid();
    }
}

Hello Friend,
                Kindly go through the following link

http://www.c-sharpcorner.com/uploadfile/17e8f6/insert-update-and-delete-in-datagrid-in-Asp-Net/

With Regards,
Vishal Gilbile.