how to display text box values in grid view on button click

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)
    {

    }
    private void BindGrid(int rowcount)
    {
        DataTable dt = new DataTable();
        DataRow dr;
        dt.Columns.Add(new System.Data.DataColumn("FIRST NAME", typeof(String)));
        dt.Columns.Add(new System.Data.DataColumn("FATHER NAME", typeof(String)));
        dt.Columns.Add(new System.Data.DataColumn("LAST NAME", typeof(String)));
        dt.Columns.Add(new System.Data.DataColumn("AGE", typeof(String)));
        dt.Columns.Add(new System.Data.DataColumn("EMAIL", typeof(String)));
        dt.Columns.Add(new System.Data.DataColumn("TELEPHONE", typeof(String)));

        if (ViewState["CurrentData"] != null)
        {
            for (int i = 0; i < rowcount + 1; i++)
            {
                dt = (DataTable)ViewState["CurrentData"];
                if (dt.Rows.Count > 0)
                {
                    dr = dt.NewRow();
                    dr[0] = dt.Rows[0][0].ToString();

                }
            }
            dr = dt.NewRow();
            dr[0] = txtname.Text;
            dr[1] = txtfname.Text;
            dr[2] = txtlname.Text;
            dr[3] = txtage.Text;
            dr[4] = txtemail.Text;
            dr[5] = txttele.Text;

            dt.Rows.Add(dr);

        }
        else
        {
            dr = dt.NewRow();
            dr[0] = txtname.Text;
            dr[1] = txtfname.Text;
            dr[2] = txtlname.Text;
            dr[3] = txtage.Text;
            dr[4] = txtemail.Text;
            dr[5] = txttele.Text;

            dt.Rows.Add(dr);

        }

        // If ViewState has a data then use the value as the DataSource
        if (ViewState["CurrentData"] != null)
        {
            GridView1.DataSource = (DataTable)ViewState["CurrentData"];
            GridView1.DataBind();
        }
        else
        {
            // Bind GridView with the initial data assocaited in the DataTable
            GridView1.DataSource = dt;
            GridView1.DataBind();

        }
        // Store the DataTable in ViewState to retain the values
        ViewState["CurrentData"] = dt;

    }

    protected void btnadd_Click(object sender, EventArgs e)
    {
        // Check if the ViewState has a data assoiciated within it. If
        if (ViewState["CurrentData"] != null)
        {
            DataTable dt = (DataTable)ViewState["CurrentData"];
            int count = dt.Rows.Count;
            BindGrid(count);
        }
        else
        {
            BindGrid(1);
        }
        txtname.Text = string.Empty;
        txtfname.Text = string.Empty;
        txtlname.Text = string.Empty;
        txtage.Text = string.Empty;
        txtemail.Text = string.Empty;
        txttele.Text = string.Empty;

        txtname.Focus();
        txtfname.Focus();
        txtlname.Focus();
        txtage.Focus();
        txtemail.Focus();
        txttele.Focus();
        
    }
}