I have a problem when select record by mouse click didn't accept update record in datagrid view

int x;

da.UpdateCommand = new SqlCommand("update tblcontacts set firstname=@firstname,lastname=@lastname where id=@id ", cs);
da.UpdateCommand.Parameters.Add("@firstname", SqlDbType.VarChar).Value = textBox1.Text;
da.UpdateCommand.Parameters.Add("@lastname", SqlDbType.VarChar).Value = textBox2.Text;
da.UpdateCommand.Parameters.Add("@id", SqlDbType.BigInt).Value = ds.Tables[0].Rows[tblnamesbs.Position][0];

cs.Open();
x= da.UpdateCommand.ExecuteNonQuery();
cs.Close();

if (x >= 1)
    MessageBox.Show("Record(s) has been updated");

da.SelectCommand = new SqlCommand("select * from tblcontacts ", cs);
ds.Clear();
da.Fill(ds);

dt=ds.Tables[0];
dataGridView1.DataSource = ds.Tables[0];
//DataTable dt = new DataTable();

//dt.Columns.Add("firstname", typeof(string));
//dt.Columns.Add("lastname", typeof(string));

tblnamesbs.DataSource = dt;
this.textBox1.DataBindings.Clear();
this.textBox1.DataBindings.Add("Text", this.tblnamesbs, "firstname", true);
this.textBox2.DataBindings.Clear();
this.textBox2.DataBindings.Add("Text", this.tblnamesbs, "lastname", true);
records();

tblnamesbs.DataSource = dt;
            tblnamesbs.MoveFirst();
            dgupdate();
            records();