Please refer this article
Instead of displaying the data in Textboxes you can insert the particular row in Database table.
protected void OnSelectedIndexChanged(object sender, EventArgs e)
{
GridViewRow row = GridView1.SelectedRow;
string id = row.Cells[0].Text;
string name = row.Cells[1].Text;
string country = (row.FindControl("lblCountry") as Label).Text;
this.Save(id, name, country);
}
private void Save(string id, string name, string coutry)
{
//Save these variables in Database
}