How to add selected row from one gridview to another gridview?

<asp:GridView ID="GridView1" runat="server" DataKeyNames="pid" AutoGenerateColumns="false"
    OnPageIndexChanging="GridView1_PageIndexChanging" OnRowCommand="GridView1_RowCommand">
    <Columns>
        <asp:BoundField DataField="pid" HeaderText="product id." />
        <asp:BoundField DataField="pname" HeaderText="product Name" />
        <asp:BoundField DataField="price" HeaderText="price" />
        <asp:TemplateField HeaderText="Details">
            <ItemTemplate>
                <asp:LinkButton ID="lnkDet" CommandName="cmdBind" CommandArgument="<%# ((GridViewRow) Container).RowIndex %>"
                    runat="server" CausesValidation="false">select product</asp:LinkButton>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>
<asp:GridView ID="GridView2" runat="server" DataKeyNames="pid" AutoGenerateColumns="false">
    <Columns>
        <asp:BoundField DataField="pid" HeaderText="product id." />
        <asp:BoundField DataField="pname" HeaderText="product Name" />
        <asp:BoundField DataField="price" HeaderText="price" />
    </Columns>
</asp:GridView><br />

using System.Data;
using System.Data.SqlClient;
using System.Configuration;

public partial class _Default : System.Web.UI.Page
{
    SqlConnection sqlcon = new SqlConnection(ConfigurationManager.ConnectionStrings["Con"].ConnectionString);
    SqlCommand sqlcmd;
    SqlDataAdapter da;
    DataTable dt = new DataTable();
    DataTable dt1 = new DataTable();
    DataRow dr;

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            GridData();
            dt1.Columns.Add("pid");
            dt1.Columns.Add("pname");
            dt1.Columns.Add("price");
            Session["dt"] = dt1;
        }
    }
    //Refresh gridview using below method
    void GridData()
    {
        sqlcmd = new SqlCommand("select * from product", sqlcon);
        sqlcon.Open();
        da = new SqlDataAdapter(sqlcmd);
        dt.Clear();
        da.Fill(dt);
        if (dt.Rows.Count > 0)
        {
            GridView1.DataSource = dt;
            GridView1.DataBind();
        }
    }

    protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        GridView1.PageIndex = e.NewPageIndex;
        GridData();
    }
    //If user click select in gridview then that row valuse insert into the second grid
    protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "cmdBind")
        {
            LinkButton lb = (LinkButton)e.CommandSource;
            int index = Convert.ToInt32(lb.CommandArgument);
            dt1 = (DataTable)Session["dt"];
            dr = dt1.NewRow();
            dr["pid"] = GridView1.Rows[index].Cells[0].Text;
            dr["pname"] = GridView1.Rows[index].Cells[1].Text;
            dr["price"] = GridView1.Rows[index].Cells[2].Text;
            dt1.Rows.Add(dr);
            Session["dt"] = dt1;
            GridView2.DataSource = dt1;
            GridView2.DataBind();
        }
    }
}