loading data into datagrid

public void bindgrid()
{
//your code here.
}
and call it in page load event
if(!ispostback)
{
bindgrid();
}

protected void Page_Load(object sender, EventArgs e)
       {
           if (!Page.IsPostBack)
           {
               DataTable dtToGrid = new DataTable();
               dtToGrid.Columns.Add("UserName", typeof(string));
               dtToGrid.Columns.Add("Password", typeof(string));
               Session["dtToGrid"] = dtToGrid;
           }
       }
       protected void Button1_Click(object sender, EventArgs e)
       {
          //to show textboxes data in gridview
           DataTable dtToGrid = (DataTable)Session["dtToGrid"];
           DataRow drToGrid = dtToGrid.NewRow();
           drToGrid["UserName"] = TextBox1.Text.Trim();
           drToGrid["Password"] = TextBox2.Text.Trim();
           dtToGrid.Rows.Add(drToGrid);
           GridView1.DataSource = dtToGrid;
           GridView1.DataBind();
           TextBox1.Text = "";
       }
       protected void Button2_Click(object sender, EventArgs e)
       {
           //save in Sql Server Table
           cn.Open();
           DataTable dt = (DataTable)Session["dtToGrid"];
           using (SqlBulkCopy copy = new SqlBulkCopy(cn))
           {
               copy.DestinationTableName = "userdetails";
              copy.WriteToServer(dt);
           }
           Page.RegisterStartupScript("<script>", "<script>alert('Successfully Saved')</script>");

       }