txtBOX文本框绑定后,为何不随DataGrid,comboBox连动?谢谢指导

private void Form1_Load(object sender, System.EventArgs e)
{
SqlConnection objConn = new SqlConnection();
SqlCommand objComm = new SqlCommand();
SqlDataAdapter objDa = new SqlDataAdapter();
DataSet objDs = new DataSet(); objConn.ConnectionString = "Data Source=(local);Initial Catalog=Northwind;Integrated Security=SSPI";
objComm.CommandText = "Select * From Products";
objComm.Connection = objConn;
objDa.SelectCommand = objComm;
objConn.Open();
objDa.Fill(objDs, "products");
objConn.Close();
dataGrid1.DataSource = objDs.Tables["products"]; //combox methed 2 ok.
this.comboBox1.DataSource = objDs.Tables["products"];        
    this.comboBox1.DisplayMember = "ProductName";            
    this.textBox1.DataBindings.Add("Text", objDs, "products.ProductName"); this.listBox1.DataSource = objDs.Tables["products"];
this.listBox1.DisplayMember = "UnitPrice";
this.listBox1.ValueMember = "UnitPrice"; }
由于我是初学者,敬请各位指导谢谢.