Populate data in gridview using datatable[SELECT,EDIT,UPDATE,CANCEL]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;

public partial class _Default : System.Web.UI.Page
{
 
 
 
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("Name");
            dt.Columns.Add("Age");
            dt.Columns.Add("Sex");

            dt.Rows.Add("Anurag", "24", "M");
            dt.Rows.Add("Ruchi", "23", "F");
            dt.Rows.Add("Abhi", "22", "M");

            GridView1.DataSource = dt;
            GridView1.DataBind();

        }
    }


    protected void Button1_Click(object sender, EventArgs e)
    {

    }
}

-------------------------------------SELECT IN GRID VIEW-------------------------

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;

public partial class _Default : System.Web.UI.Page
{
 
 
 
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("Name");
            dt.Columns.Add("Age");
            dt.Columns.Add("Sex");

            dt.Rows.Add("Anurag", "24", "M");
            dt.Rows.Add("Ruchi", "23", "F");
            dt.Rows.Add("Abhi", "22", "M");

            GridView1.DataSource = dt;
            GridView1.DataBind();

        }
    }


    protected void Button1_Click(object sender, EventArgs e)
    {

    }
    protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
    {

    }
    protected void GridView1_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
    {

    }
    protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {

    }
    protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "Select")
        {

            int num = Convert.ToInt32(e.CommandArgument);

            TextName.Text= GridView1.Rows[num].Cells[2].Text;
            TextAge.Text=  GridView1.Rows[num].Cells[3].Text;
            TextSex.Text = GridView1.Rows[num].Cells[4].Text;
     
        }
    }
}

--SECOND ROW SELECTED

----------------------------EDIT/UPDATE/CANCEL----------------------------------------------------

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;

public partial class _Default : System.Web.UI.Page
{

    public DataTable dtviewstate
    {

        get
        {
            return (DataTable)ViewState["dtview"];
        }

        set
       
        {

            ViewState["dtview"] = value;
        }
 
   
    }
   
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("Name");
            dt.Columns.Add("Age");
            dt.Columns.Add("Sex");

            dt.Rows.Add("Anurag", "24", "M");
            dt.Rows.Add("Ruchi", "23", "F");
            dt.Rows.Add("Abhi", "22", "M");

            dtviewstate = dt;
            GridView1.DataSource = dt;
            GridView1.DataBind();

        }
    }


    protected void Button1_Click(object sender, EventArgs e)
    {

    }
    protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
    {
        GridView1.EditIndex = e.NewEditIndex;
        HiddenField1.Value = e.NewEditIndex.ToString();
        GridView1.DataSource = dtviewstate;
        GridView1.DataBind();

    }
    protected void GridView1_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
    {
        GridView1.EditIndex = -1;
        GridView1.DataSource = dtviewstate;
        GridView1.DataBind();

    }
    protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        TextBox t1 = new TextBox();
        TextBox t2 = new TextBox();
        TextBox t3 = new TextBox();

        t1 = (TextBox)GridView1.Rows[Convert.ToInt32( HiddenField1.Value)].Cells[2].Controls[0];
        t2 = (TextBox)GridView1.Rows[Convert.ToInt32(HiddenField1.Value)].Cells[3].Controls[0];
        t3 = (TextBox)GridView1.Rows[Convert.ToInt32(HiddenField1.Value)].Cells[4].Controls[0];


        dtviewstate.Rows[e.RowIndex]["Name"]=t1.Text;
        dtviewstate.Rows[e.RowIndex]["Age"]=t2.Text;
        dtviewstate.Rows[e.RowIndex]["Sex"]=t3.Text;

        GridView1.EditIndex = -1;
        GridView1.DataSource = dtviewstate;
        GridView1.DataBind();
   
   
   
   
    }
    protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "Select")
        {

            int num = Convert.ToInt32(e.CommandArgument);

            TextName.Text = GridView1.Rows[num].Cells[2].Text;
            TextAge.Text=  GridView1.Rows[num].Cells[3].Text;
            TextSex.Text = GridView1.Rows[num].Cells[4].Text;
       
        }
    }
}