private DemoEntities db = new DemoEntities();

    protected void Page_Load(object sender, EventArgs e)

    {

    }

    protected void Button1_Click(object sender, EventArgs e)

    {

        GridView1.DataSource = db.personMains;// select * from Personmains

        GridView1.DataBind();

    }

    protected void Button2_Click(object sender, EventArgs e)

    {

        GridView1.DataSource = db.personMains.Where(em => em.ID ==1);

        GridView1.DataBind();

    }

    protected void Button3_Click(object sender, EventArgs e)

    {

        personMain pm = new personMain();

        pm.Name = TextBox1.Text;

        db.AddTopersonMains(pm);//add object of personmain to db

        db.SaveChanges(); // db save changes

    }

    protected void Button4_Click(object sender, EventArgs e)

    {

        int IDs = Convert.ToInt32(TextBox1.Text);

        personMain pmt = db.personMains.Where(em => em.ID == IDs).First();

        db.DeleteObject(pmt);

        db.SaveChanges();

    }

    protected void Button5_Click(object sender, EventArgs e)

    {

        int IDS = Convert.ToInt32(TextBox1.Text);

        personMain pmt = db.personMains.Where(emt => emt.ID == IDS).First();

        pmt.Name = TextBox2.Text;

        db.SaveChanges();

    }